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\n  \n 2023\n \n \n (4)\n \n \n
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\n \n\n \n \n \n \n \n Superplastic behavior of Al15(CuFeMn)85 immiscible medium-entropy alloy.\n \n \n \n\n\n \n Park, H.; Thi-Cam Nguyen, N.; Sathiyamoorthi, P.; Son, S.; Moon, J.; and Kim, H.\n\n\n \n\n\n\n Intermetallics, 157. 2023.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Superplastic behavior of Al<inf>15</inf>(CuFeMn)<inf>85</inf> immiscible medium-entropy alloy},\n type = {article},\n year = {2023},\n keywords = {High-entropy alloys,Microstructure,Severe plastic deformation,Superplasticity},\n volume = {157},\n id = {6cdd2e92-f3f5-351e-8d9d-c805feb835e1},\n created = {2023-04-03T07:19:20.226Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2023-04-03T07:19:20.226Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In this study, the superplastic behavior and microstructural characteristics of the high pressure torsion-processed Al15(CuFeMn)85 immiscible medium-entropy alloy (IMMEA) were investigated. The multi-phase structure generated through spinodal-like decomposition in IMMEA played a key role in maintaining the ultra-fine structure and preserving an equiaxed shape during testing at high temperatures, ultimately leading to superplastic behavior. The IMMEA exhibited ∼460% superplasticity at a strain rate of 10−3 s−1 and a temperature of 873 K (0.56 homologous temperature). This study is the first IMMEA superplasticity study and these results contribute to a better comprehension of the phenomenon.},\n bibtype = {article},\n author = {Park, H. and Thi-Cam Nguyen, N. and Sathiyamoorthi, P. and Son, S. and Moon, J. and Kim, H.S.},\n doi = {10.1016/j.intermet.2023.107883},\n journal = {Intermetallics}\n}
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\n In this study, the superplastic behavior and microstructural characteristics of the high pressure torsion-processed Al15(CuFeMn)85 immiscible medium-entropy alloy (IMMEA) were investigated. The multi-phase structure generated through spinodal-like decomposition in IMMEA played a key role in maintaining the ultra-fine structure and preserving an equiaxed shape during testing at high temperatures, ultimately leading to superplastic behavior. The IMMEA exhibited ∼460% superplasticity at a strain rate of 10−3 s−1 and a temperature of 873 K (0.56 homologous temperature). This study is the first IMMEA superplasticity study and these results contribute to a better comprehension of the phenomenon.\n
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\n \n\n \n \n \n \n \n Cryogenic tensile behavior of laser additive manufactured CoCrFeMnNi high entropy alloys.\n \n \n \n\n\n \n Kim, E.; Ramkumar, K.; Karthik, G.; Jeong, S.; Ahn, S.; Sathiyamoorthi, P.; Park, H.; Heo, Y.; and Kim, H.\n\n\n \n\n\n\n Journal of Alloys and Compounds, 942. 2023.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Cryogenic tensile behavior of laser additive manufactured CoCrFeMnNi high entropy alloys},\n type = {article},\n year = {2023},\n keywords = {Cryogenic tensile properties,Deformation twinning,Direct energy deposition,High entropy alloy,Laser powder bed fusion},\n volume = {942},\n id = {648160a3-34e7-3c39-aef2-5d038778525b},\n created = {2023-04-03T07:19:20.230Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2023-04-03T07:19:20.230Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the present work the microstructural evolution, tensile properties, and deformation behavior of additively manufactured equiatomic CoCrFeMnNi high entropy alloy (HEA) were investigated at a cryogenic temperature (77 K). Metal additive manufacturing components are known to have exceptional yield strength, without compromising ductility. Here, laser powder bed fusion (LPBF) and direct energy deposition (DED) additive manufacturing processes were chosen as the fabrication techniques and wrought CoCrFeMnNi HEA was also fabricated for comparison. The tensile behaviors at different temperatures (298 K and 77 K) indicated temperature-dependent strength and ductility in all the samples. In particular, the HEA processed by DED exhibited excellent strength and ductility, with exceptional strain hardening, compared to the LPBF and wrought samples at 77 K. Post-tensile microstructures revealed the formation of deformation twinning in addition to dislocation slip as deformation mechanism at 77 K. Our results suggest that cellular structure plays an essential role in yield strength. Moreover, the interactions of the deformation twins and cellular dislocation structures increase strain hardening and help retard plastic instability, thereby improving ductility at 77 K.},\n bibtype = {article},\n author = {Kim, E.S. and Ramkumar, K.R. and Karthik, G.M. and Jeong, S.G. and Ahn, S.Y. and Sathiyamoorthi, P. and Park, H. and Heo, Y.-U. and Kim, H.S.},\n doi = {10.1016/j.jallcom.2023.169062},\n journal = {Journal of Alloys and Compounds}\n}
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\n In the present work the microstructural evolution, tensile properties, and deformation behavior of additively manufactured equiatomic CoCrFeMnNi high entropy alloy (HEA) were investigated at a cryogenic temperature (77 K). Metal additive manufacturing components are known to have exceptional yield strength, without compromising ductility. Here, laser powder bed fusion (LPBF) and direct energy deposition (DED) additive manufacturing processes were chosen as the fabrication techniques and wrought CoCrFeMnNi HEA was also fabricated for comparison. The tensile behaviors at different temperatures (298 K and 77 K) indicated temperature-dependent strength and ductility in all the samples. In particular, the HEA processed by DED exhibited excellent strength and ductility, with exceptional strain hardening, compared to the LPBF and wrought samples at 77 K. Post-tensile microstructures revealed the formation of deformation twinning in addition to dislocation slip as deformation mechanism at 77 K. Our results suggest that cellular structure plays an essential role in yield strength. Moreover, the interactions of the deformation twins and cellular dislocation structures increase strain hardening and help retard plastic instability, thereby improving ductility at 77 K.\n
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\n \n\n \n \n \n \n \n Editorial: High entropy alloy design concept enabled emerging novel materials with enhanced mechanical properties.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Chawake, N.; Zargaran, A.; and Kottada, R.\n\n\n \n\n\n\n Frontiers in Materials, 10. 2023.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Editorial: High entropy alloy design concept enabled emerging novel materials with enhanced mechanical properties},\n type = {article},\n year = {2023},\n keywords = {CALPHAD,alloy design,atomistic Simulations,corrosion,high entropy alloys (HEA),mechanical properties,multicomponent alloy},\n volume = {10},\n id = {a8d9d508-6de4-30d2-8678-f49794199d37},\n created = {2023-04-03T07:19:20.315Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2023-04-03T07:19:20.315Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Chawake, N. and Zargaran, A. and Kottada, R.S.},\n doi = {10.3389/fmats.2023.1162346},\n journal = {Frontiers in Materials}\n}
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\n \n\n \n \n \n \n \n High-density nanoprecipitates and phase reversion via maraging enable ultrastrong yet strain-hardenable medium-entropy alloy.\n \n \n \n\n\n \n Kwon, H.; Sathiyamoorthi, P.; Gangaraju, M.; Zargaran, A.; Wang, J.; Heo, Y.; Harjo, S.; Gong, W.; Lee, B.; and Kim, H.\n\n\n \n\n\n\n Acta Materialia, 248. 2023.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {High-density nanoprecipitates and phase reversion via maraging enable ultrastrong yet strain-hardenable medium-entropy alloy},\n type = {article},\n year = {2023},\n keywords = {Maraging medium-entropy alloy,Martensitic phase transformation,Mechanical properties,Precipitation strengthening,Strain hardening},\n volume = {248},\n id = {3b3a8683-eaca-3f52-bfb4-1df60683e27a},\n created = {2023-04-03T07:19:20.327Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2023-04-03T07:19:20.327Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Maraging steels, known for ultrahigh strength and good fracture toughness, derive their superior properties from lath martensite structure with high-density nanoprecipitates. In this work, we designed a novel Fe-based medium-entropy alloy with a chemical composition of Fe60Co25Ni10Mo5 in atomic% (at%) by utilizing the characteristics of the maraging steels. By a single-step aging of only 10 min at 650 ℃, the alloy showed microstructures consisting of a very high number density of (Fe, Co, Ni)7Mo6-type nanoprecipitates in lath martensite structure and reverted FCC phase, which led to ultrahigh yield strength higher than 2 GPa. Additionally, the alloy exhibited a high ultimate tensile strength of ∼2.2 GPa and uniform ductility of ∼6% by harnessing deformation-induced martensitic transformation of the reverted FCC to BCC martensite, which has hardly been exploited in conventional maraging steels. This work demonstrates a novel direction to produce strong and ductile materials by expanding the horizons of material design with the aid of high-entropy concept and overcoming the limits of conventional materials.},\n bibtype = {article},\n author = {Kwon, H. and Sathiyamoorthi, P. and Gangaraju, M.K. and Zargaran, A. and Wang, J. and Heo, Y.-U. and Harjo, S. and Gong, W. and Lee, B.-J. and Kim, H.S.},\n doi = {10.1016/j.actamat.2023.118810},\n journal = {Acta Materialia}\n}
\n
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\n Maraging steels, known for ultrahigh strength and good fracture toughness, derive their superior properties from lath martensite structure with high-density nanoprecipitates. In this work, we designed a novel Fe-based medium-entropy alloy with a chemical composition of Fe60Co25Ni10Mo5 in atomic% (at%) by utilizing the characteristics of the maraging steels. By a single-step aging of only 10 min at 650 ℃, the alloy showed microstructures consisting of a very high number density of (Fe, Co, Ni)7Mo6-type nanoprecipitates in lath martensite structure and reverted FCC phase, which led to ultrahigh yield strength higher than 2 GPa. Additionally, the alloy exhibited a high ultimate tensile strength of ∼2.2 GPa and uniform ductility of ∼6% by harnessing deformation-induced martensitic transformation of the reverted FCC to BCC martensite, which has hardly been exploited in conventional maraging steels. This work demonstrates a novel direction to produce strong and ductile materials by expanding the horizons of material design with the aid of high-entropy concept and overcoming the limits of conventional materials.\n
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\n  \n 2022\n \n \n (9)\n \n \n
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\n \n\n \n \n \n \n \n Publisher Correction: Ultrahigh high-strain-rate superplasticity in a nanostructured high-entropy alloy (Nature Communications, (2020), 11, 1, (2736), 10.1038/s41467-020-16601-1).\n \n \n \n\n\n \n Nguyen, N.; Asghari-Rad, P.; Sathiyamoorthi, P.; Zargaran, A.; Lee, C.; and Kim, H.\n\n\n \n\n\n\n Nature Communications, 13(1). 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
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@article{\n title = {Publisher Correction: Ultrahigh high-strain-rate superplasticity in a nanostructured high-entropy alloy (Nature Communications, (2020), 11, 1, (2736), 10.1038/s41467-020-16601-1)},\n type = {article},\n year = {2022},\n volume = {13},\n id = {d2476cd8-2211-3173-a980-3cc314da0383},\n created = {2022-09-07T04:57:19.059Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.059Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The original version of this Article contained an error in Figure 2, where the horizontal axis value ‘1600’ in panel (a) was incorrectly labelled as ‘1200’. This has now been corrected in both the PDF and HTML versions of the Article.},\n bibtype = {article},\n author = {Nguyen, N.T.-C. and Asghari-Rad, P. and Sathiyamoorthi, P. and Zargaran, A. and Lee, C.S. and Kim, H.S.},\n doi = {10.1038/s41467-022-28422-5},\n journal = {Nature Communications},\n number = {1}\n}
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\n The original version of this Article contained an error in Figure 2, where the horizontal axis value ‘1600’ in panel (a) was incorrectly labelled as ‘1200’. This has now been corrected in both the PDF and HTML versions of the Article.\n
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\n \n\n \n \n \n \n \n Relation of phase fraction to superplastic behavior of multi-principal element alloy with a multi-phase structure.\n \n \n \n\n\n \n Nguyen, N.; Asghari-Rad, P.; Zargaran, A.; Kim, E.; Sathiyamoorthi, P.; and Kim, H.\n\n\n \n\n\n\n Scripta Materialia, 221. 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Relation of phase fraction to superplastic behavior of multi-principal element alloy with a multi-phase structure},\n type = {article},\n year = {2022},\n keywords = {High-entropy alloy,High-strain rate superplasticity,Multi-phase structure,Phase fraction,Superplasticity},\n volume = {221},\n id = {2ad623d5-367c-353e-b712-59a3e54fac4c},\n created = {2022-09-07T04:57:19.060Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.060Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {An Al0.3CoCrNi medium-entropy alloy was annealed in two conditions to differentiate the phase fraction of nano-scaled B2 and sigma precipitates in FCC microstructure, processed by high-pressure torsion, and subjected to a superplasticity test. The Al0.3CoCrNi with different microstructure exhibited distinct superplastic performance, with maximum elongation of 1900% and 1735% from tensile deformation at 1073 K at the strain rate at 5 × 10−3 s−1 and 10−2 s−1, respectively. The microstructural analysis revealed that the superplasticity is dominantly governed by the grain boundary sliding mechanism with the accommodation of intragranular dislocations. The Al0.3CoCrNi alloy, after superplastic deformation, consists of the mixture of FCC, B2, and sigma phases with different phase fractions. The comparison of this multi-phase structured alloy at two conditions and the sister alloy, Al0.5CoCrFeMnNi high-entropy alloy, suggests that increment of B2 and sigma phase fraction is beneficial to promote high-strain rate superplasticity by limiting the grain growth.},\n bibtype = {article},\n author = {Nguyen, N.T.-C. and Asghari-Rad, P. and Zargaran, A. and Kim, E.S. and Sathiyamoorthi, P. and Kim, H.S.},\n doi = {10.1016/j.scriptamat.2022.114949},\n journal = {Scripta Materialia}\n}
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\n An Al0.3CoCrNi medium-entropy alloy was annealed in two conditions to differentiate the phase fraction of nano-scaled B2 and sigma precipitates in FCC microstructure, processed by high-pressure torsion, and subjected to a superplasticity test. The Al0.3CoCrNi with different microstructure exhibited distinct superplastic performance, with maximum elongation of 1900% and 1735% from tensile deformation at 1073 K at the strain rate at 5 × 10−3 s−1 and 10−2 s−1, respectively. The microstructural analysis revealed that the superplasticity is dominantly governed by the grain boundary sliding mechanism with the accommodation of intragranular dislocations. The Al0.3CoCrNi alloy, after superplastic deformation, consists of the mixture of FCC, B2, and sigma phases with different phase fractions. The comparison of this multi-phase structured alloy at two conditions and the sister alloy, Al0.5CoCrFeMnNi high-entropy alloy, suggests that increment of B2 and sigma phase fraction is beneficial to promote high-strain rate superplasticity by limiting the grain growth.\n
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\n \n\n \n \n \n \n \n Role of cellular structure on deformation twinning and hetero-deformation induced strengthening of laser powder-bed fusion processed CuSn alloy.\n \n \n \n\n\n \n Karthik, G.; Kim, E.; Zargaran, A.; Sathiyamoorthi, P.; Jeong, S.; and Kim, H.\n\n\n \n\n\n\n Additive Manufacturing, 54. 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Role of cellular structure on deformation twinning and hetero-deformation induced strengthening of laser powder-bed fusion processed CuSn alloy},\n type = {article},\n year = {2022},\n keywords = {Cellular structure,CuSn alloy,Deformation behavior,Deformation twinning,Hetero-deformation induced strengthening,Laser powder-bed fusion},\n volume = {54},\n id = {713713b1-8484-3936-a762-6d371d7b2817},\n created = {2022-09-07T04:57:19.122Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.122Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The sub-grain cellular dislocation structure has been reported to be the primary reason for the enhanced mechanical properties in laser powder-bed fusion (LPBF) parts. In the current work, the contribution of the cellular dislocation structure to the yield strength of LPBF processed CuSn alloy is estimated to be ~45%. In addition, this work shows that the cellular dislocation structure significantly controls the deformation behavior of LPBF processed CuSn alloy by suppressing the formation of deformation twinning. Post-LPBF heat treatment with fully recrystallized microstructures devoid of cellular dislocation structure showed pronounced twinning activity. The reduced homogeneous slip length due to the fine dislocation cell structure ~600 nm and increased stacking fault energy due to the cellular Sn segregation significantly increased the activation energy for the nucleation and propagation of the partial dislocations and suppressed the deformation twinning in the as-built samples. Furthermore, the present work shows that cellular dislocation structure contributes significantly to the hetero-deformation induced strengthening, much higher than the heterogeneous grain structure in the LPBF samples.},\n bibtype = {article},\n author = {Karthik, G.M. and Kim, E.S. and Zargaran, A. and Sathiyamoorthi, P. and Jeong, S.G. and Kim, H.S.},\n doi = {10.1016/j.addma.2022.102744},\n journal = {Additive Manufacturing}\n}
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\n The sub-grain cellular dislocation structure has been reported to be the primary reason for the enhanced mechanical properties in laser powder-bed fusion (LPBF) parts. In the current work, the contribution of the cellular dislocation structure to the yield strength of LPBF processed CuSn alloy is estimated to be ~45%. In addition, this work shows that the cellular dislocation structure significantly controls the deformation behavior of LPBF processed CuSn alloy by suppressing the formation of deformation twinning. Post-LPBF heat treatment with fully recrystallized microstructures devoid of cellular dislocation structure showed pronounced twinning activity. The reduced homogeneous slip length due to the fine dislocation cell structure ~600 nm and increased stacking fault energy due to the cellular Sn segregation significantly increased the activation energy for the nucleation and propagation of the partial dislocations and suppressed the deformation twinning in the as-built samples. Furthermore, the present work shows that cellular dislocation structure contributes significantly to the hetero-deformation induced strengthening, much higher than the heterogeneous grain structure in the LPBF samples.\n
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\n \n\n \n \n \n \n \n 1.7 Gpa tensile strength in ferrous medium entropy alloy via martensite and precipitation.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Asghari-Rad, P.; Zargaran, A.; Manogna Karthik, G.; Kwon, H.; and Kim, H.\n\n\n \n\n\n\n Materials Letters, 307. 2022.\n \n\n\n\n
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@article{\n title = {1.7 Gpa tensile strength in ferrous medium entropy alloy via martensite and precipitation},\n type = {article},\n year = {2022},\n keywords = {Hot rolling,Lath martensite,Medium-entropy alloys,Precipitation,Tensile strength},\n volume = {307},\n id = {93c30880-1b00-3ac2-b73a-97c9cbb33a74},\n created = {2022-09-07T04:57:19.137Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.137Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A Fe50Co25Ni10Al5Ti5Mo5 medium entropy alloy was fabricated through the casting route and processed by hot rolling and heat treatment to achieve high strength via martensitic structure and precipitation. The hot-rolled plate heat-treated at 1000 °C for 10 min exhibited fine lath martensite structure, two kind of precipitates, retained FCC phase, and high dislocation density. The sample with this complex microstructure exhibited superior tensile properties with an extremely high tensile strength of ∼ 1.7 GPa and a good uniform elongation of ∼ 8%.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Asghari-Rad, P. and Zargaran, A. and Manogna Karthik, G. and Kwon, H. and Kim, H.S.},\n doi = {10.1016/j.matlet.2021.130958},\n journal = {Materials Letters}\n}
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\n A Fe50Co25Ni10Al5Ti5Mo5 medium entropy alloy was fabricated through the casting route and processed by hot rolling and heat treatment to achieve high strength via martensitic structure and precipitation. The hot-rolled plate heat-treated at 1000 °C for 10 min exhibited fine lath martensite structure, two kind of precipitates, retained FCC phase, and high dislocation density. The sample with this complex microstructure exhibited superior tensile properties with an extremely high tensile strength of ∼ 1.7 GPa and a good uniform elongation of ∼ 8%.\n
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\n \n\n \n \n \n \n \n Deformation-induced grain boundary segregation mediated high-strain rate superplasticity in medium entropy alloy.\n \n \n \n\n\n \n Asghari-Rad, P.; Nguyen, N.; Zargaran, A.; Sathiyamoorthi, P.; and Kim, H.\n\n\n \n\n\n\n Scripta Materialia, 207. 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Deformation-induced grain boundary segregation mediated high-strain rate superplasticity in medium entropy alloy},\n type = {article},\n year = {2022},\n keywords = {Deformation-induced segregation,High strain-rate superplasticity,Multi-principal element alloys,Partial melting,Severe plastic deformation},\n volume = {207},\n id = {e0757628-dd91-3349-bef4-1f4cf1c56ca1},\n created = {2022-09-07T04:57:19.200Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.200Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Superplasticity refers to extremely high plastic deformation of crystalline materials at homologous temperature. In particular, high-strain rate superplasticity (HSRS) at a strain rate equal to or higher than 10−2 s−1 draws great technological interest in the shape-forming of engineering materials. Besides primary mechanism as grain boundary sliding, the formation of liquid phase at grain boundaries/interfaces can assist HSRS. With the advent of multi-principle element alloys (MPEAs), designing grain boundary segregation of a low melting temperature element with the appropriate choice of composition can bring the possibility to produce the HSRS accommodated by the partial melting in MPEAs. Here, we show the trace of the liquid phase in Al0.3CoCrNi MPEA at the homologous temperature of 0.65. Careful microstructural examination reveals for the first time that deformation-induced Al-segregation occurs at grain boundaries/interfaces. The present work expedites a new path to tailoring microstructure for promoting the HSRS in high-strength materials by grain boundary segregation engineering.},\n bibtype = {article},\n author = {Asghari-Rad, P. and Nguyen, N.T.-C. and Zargaran, A. and Sathiyamoorthi, P. and Kim, H.S.},\n doi = {10.1016/j.scriptamat.2021.114239},\n journal = {Scripta Materialia}\n}
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\n Superplasticity refers to extremely high plastic deformation of crystalline materials at homologous temperature. In particular, high-strain rate superplasticity (HSRS) at a strain rate equal to or higher than 10−2 s−1 draws great technological interest in the shape-forming of engineering materials. Besides primary mechanism as grain boundary sliding, the formation of liquid phase at grain boundaries/interfaces can assist HSRS. With the advent of multi-principle element alloys (MPEAs), designing grain boundary segregation of a low melting temperature element with the appropriate choice of composition can bring the possibility to produce the HSRS accommodated by the partial melting in MPEAs. Here, we show the trace of the liquid phase in Al0.3CoCrNi MPEA at the homologous temperature of 0.65. Careful microstructural examination reveals for the first time that deformation-induced Al-segregation occurs at grain boundaries/interfaces. The present work expedites a new path to tailoring microstructure for promoting the HSRS in high-strength materials by grain boundary segregation engineering.\n
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\n \n\n \n \n \n \n \n The influence of laser powder-bed fusion microstructures on the corrosion behavior of CuSn alloy.\n \n \n \n\n\n \n Karthik, G.; Haftlang, F.; Kwak, J.; Sathiyamoorthi, P.; Zargaran, A.; Kim, Y.; and Kim, H.\n\n\n \n\n\n\n Journal of Materials Science. 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
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@article{\n title = {The influence of laser powder-bed fusion microstructures on the corrosion behavior of CuSn alloy},\n type = {article},\n year = {2022},\n id = {dc0fe71c-7976-3c42-a97e-ed62d645c748},\n created = {2022-09-07T04:57:19.207Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.207Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Selective laser melting (SLM), a laser powder-bed fusion technique, shows unique heterogeneous microstructures because of the complex thermal history they experience during layer-wise part fabrication. The current work attempts to establish the influence of these microstructures on the corrosion behavior of the SLM processed CuSn alloy. The as-built SLM samples showed heterogeneous epitaxial columnar grains, fine cellular dislocation structure (~ 600 nm) with cell boundaries having higher dislocation density and solute Sn concentration than the cell interior, super-saturated solid-solution with ~ 6.5 wt% of Sn in Cu, and fine second-phase δ (Cu41Sn11) ~ 200 nm. The SLM microstructures affected the corrosion behavior of the CuSn alloy: the as-built samples showed high corrosion rate than the post-SLM heat-treated fully recrystallized samples. The effects of the residual stresses, cellular segregation, and second-phase δ (Cu41Sn11) on the corrosion behavior are minimal. The dislocation density and distribution primarily control the corrosion behavior of the SLM processed CuSn alloy. The partially recrystallized microstructures with heterogeneous dislocation distribution showed an increased corrosion rate.},\n bibtype = {article},\n author = {Karthik, G.M. and Haftlang, F. and Kwak, J. and Sathiyamoorthi, P. and Zargaran, A. and Kim, Y.-T. and Kim, H.S.},\n doi = {10.1007/s10853-022-07137-4},\n journal = {Journal of Materials Science}\n}
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\n Selective laser melting (SLM), a laser powder-bed fusion technique, shows unique heterogeneous microstructures because of the complex thermal history they experience during layer-wise part fabrication. The current work attempts to establish the influence of these microstructures on the corrosion behavior of the SLM processed CuSn alloy. The as-built SLM samples showed heterogeneous epitaxial columnar grains, fine cellular dislocation structure (~ 600 nm) with cell boundaries having higher dislocation density and solute Sn concentration than the cell interior, super-saturated solid-solution with ~ 6.5 wt% of Sn in Cu, and fine second-phase δ (Cu41Sn11) ~ 200 nm. The SLM microstructures affected the corrosion behavior of the CuSn alloy: the as-built samples showed high corrosion rate than the post-SLM heat-treated fully recrystallized samples. The effects of the residual stresses, cellular segregation, and second-phase δ (Cu41Sn11) on the corrosion behavior are minimal. The dislocation density and distribution primarily control the corrosion behavior of the SLM processed CuSn alloy. The partially recrystallized microstructures with heterogeneous dislocation distribution showed an increased corrosion rate.\n
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\n \n\n \n \n \n \n \n High-entropy alloys with heterogeneous microstructure: Processing and mechanical properties.\n \n \n \n\n\n \n Sathiyamoorthi, P.; and Kim, H.\n\n\n \n\n\n\n Progress in Materials Science, 123. 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {High-entropy alloys with heterogeneous microstructure: Processing and mechanical properties},\n type = {article},\n year = {2022},\n keywords = {Hetero-deformation induced strengthening,Heterogeneous microstructure,High-entropy alloys,Strain hardening,Strength-ductility trade-off,Tensile behavior},\n volume = {123},\n id = {5781bcd3-b30d-3f15-b9af-7f34b2335497},\n created = {2022-09-07T04:57:19.286Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.286Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Engineering metallic materials are an essential class of materials for a variety of industrial applications due to their competitive mechanical properties, especially strength and ductility. Metallic materials with excellent mechanical properties are highly sought-after as engineering materials for various applications considering safety, environmental, and economic requirements. Thus, the development of high-performance alloys with high strength and high ductility is an unfading research topic for material scientists. The strength enhancement in metallic materials by conventional strengthening mechanisms always leads to a reduction in ductility, which is often referred to as strength-ductility trade-off. In recent decades, novel approaches to enhance strength-ductility synergy through heterogeneous microstructures, such as gradient, harmonic, lamellar, bimodal, hierarchical nanostructures, etc., have been proven to be effective in overcoming strength-ductility trade-off. However, the alloy design concept of conventional alloys limits the exploration of new alloys with good strength-ductility synergy even through heterogeneous microstructures. The discovery of a new alloy design concept based on multi-principal elements, widely known as high entropy alloys, opens up a vast compositional space and offers wider possibilities to find numerous new alloys with remarkable properties. This review article presents an overview of the mechanical behavior of high entropy alloys with heterogeneous microstructures that reconcile the strength-ductility synergy.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Kim, H.S.},\n doi = {10.1016/j.pmatsci.2020.100709},\n journal = {Progress in Materials Science}\n}
\n
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\n Engineering metallic materials are an essential class of materials for a variety of industrial applications due to their competitive mechanical properties, especially strength and ductility. Metallic materials with excellent mechanical properties are highly sought-after as engineering materials for various applications considering safety, environmental, and economic requirements. Thus, the development of high-performance alloys with high strength and high ductility is an unfading research topic for material scientists. The strength enhancement in metallic materials by conventional strengthening mechanisms always leads to a reduction in ductility, which is often referred to as strength-ductility trade-off. In recent decades, novel approaches to enhance strength-ductility synergy through heterogeneous microstructures, such as gradient, harmonic, lamellar, bimodal, hierarchical nanostructures, etc., have been proven to be effective in overcoming strength-ductility trade-off. However, the alloy design concept of conventional alloys limits the exploration of new alloys with good strength-ductility synergy even through heterogeneous microstructures. The discovery of a new alloy design concept based on multi-principal elements, widely known as high entropy alloys, opens up a vast compositional space and offers wider possibilities to find numerous new alloys with remarkable properties. This review article presents an overview of the mechanical behavior of high entropy alloys with heterogeneous microstructures that reconcile the strength-ductility synergy.\n
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\n \n\n \n \n \n \n \n Work hardening behavior of hot-rolled metastable Fe50Co25Ni10Al5Ti5Mo5 medium-entropy alloy: in situ neutron diffraction analysis.\n \n \n \n\n\n \n Kwon, H.; Harjo, S.; Kawasaki, T.; Gong, W.; Jeong, S.; Kim, E.; Sathiyamoorthi, P.; Kato, H.; and Kim, H.\n\n\n \n\n\n\n Science and Technology of Advanced Materials, 23(1). 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Work hardening behavior of hot-rolled metastable Fe<inf>50</inf>Co<inf>25</inf>Ni<inf>10</inf>Al<inf>5</inf>Ti<inf>5</inf>Mo<inf>5</inf> medium-entropy alloy: in situ neutron diffraction analysis},\n type = {article},\n year = {2022},\n keywords = {In situ neutron diffraction,lattice strain,martensitic transformation,medium-entropy alloy,phase stress,tensile strength,work hardening},\n volume = {23},\n id = {e22586e7-6aeb-38a2-8123-298c0947ec4a},\n created = {2023-01-03T17:18:24.771Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2023-01-03T17:18:24.771Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Metastability engineering is a strategy to enhance the strength and ductility of alloys via deliberately lowering phase stability and prompting deformation-induced martensitic transformation. The advantages of the strategy are widely exploited by ferrous medium-entropy alloys (MEAs) that exhibit phase transformation from metastable face-centered cubic (FCC) to hexagonal close-packed (HCP) or body-centered cubic (BCC) martensite and a significant increase in work hardening. Fe50Co25Ni10Al5Ti5Mo5 (at%) MEA is an example of such materials, which shows ~1.5 GPa of tensile strength assisted by exceptional work hardening from the deformation-induced BCC martensitic transformation. In this work, the martensitic transformation and its effect on the mechanical response of the MEA were studied by in situ neutron diffraction under tensile loading. Strain-induced BCC martensite started forming rapidly from the beginning of plastic deformation, reaching a phase fraction of ~100% when deformed to ~10% of true strain. Lattice strain and phase stress evolution indicate that stress was dynamically partitioned onto the newly formed BCC martensite, which is responsible for the work hardening response and high flow stress of the MEA. This work shows how great a role FCC to BCC martensitic transformation can play in enhancing the mechanical properties of ferrous MEAs.},\n bibtype = {article},\n author = {Kwon, H. and Harjo, S. and Kawasaki, T. and Gong, W. and Jeong, S.G. and Kim, E.S. and Sathiyamoorthi, P. and Kato, H. and Kim, H.S.},\n doi = {10.1080/14686996.2022.2122868},\n journal = {Science and Technology of Advanced Materials},\n number = {1}\n}
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\n\n\n
\n Metastability engineering is a strategy to enhance the strength and ductility of alloys via deliberately lowering phase stability and prompting deformation-induced martensitic transformation. The advantages of the strategy are widely exploited by ferrous medium-entropy alloys (MEAs) that exhibit phase transformation from metastable face-centered cubic (FCC) to hexagonal close-packed (HCP) or body-centered cubic (BCC) martensite and a significant increase in work hardening. Fe50Co25Ni10Al5Ti5Mo5 (at%) MEA is an example of such materials, which shows ~1.5 GPa of tensile strength assisted by exceptional work hardening from the deformation-induced BCC martensitic transformation. In this work, the martensitic transformation and its effect on the mechanical response of the MEA were studied by in situ neutron diffraction under tensile loading. Strain-induced BCC martensite started forming rapidly from the beginning of plastic deformation, reaching a phase fraction of ~100% when deformed to ~10% of true strain. Lattice strain and phase stress evolution indicate that stress was dynamically partitioned onto the newly formed BCC martensite, which is responsible for the work hardening response and high flow stress of the MEA. This work shows how great a role FCC to BCC martensitic transformation can play in enhancing the mechanical properties of ferrous MEAs.\n
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\n \n\n \n \n \n \n \n Gradient heterostructured laser-powder bed fusion processed CoCrFeMnNi high entropy alloy.\n \n \n \n\n\n \n Karthik, G.; Kim, Y.; Kim, E.; Zargaran, A.; Sathiyamoorthi, P.; Park, J.; Jeong, S.; Gu, G.; Amanov, A.; Ungar, T.; and Kim, H.\n\n\n \n\n\n\n Additive Manufacturing, 59. 2022.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Gradient heterostructured laser-powder bed fusion processed CoCrFeMnNi high entropy alloy},\n type = {article},\n year = {2022},\n keywords = {Dislocation-based constitutive model,Gradient structures,High entropy alloys,Laser-powder bed fusion,Ultrasonic nanocrystal surface modification},\n volume = {59},\n id = {243f6077-c02c-36f4-8389-62ce2ed02752},\n created = {2023-01-03T17:18:24.772Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2023-01-03T17:18:24.772Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Developing metal additive parts with a synergy in strength and ductility is a demanding need for many critical applications. Recently, gradient structures have been of research interest as it facilitates intrinsic synergetic strengthening. In the current work, gradient microstructures are obtained on laser-powder bed fusion processed (LPBF) CoCrFeMnNi high entropy alloy using ultrasonic nanocrystal surface modification (UNSM). The UNSM treatment resulted in a thin layer of gradient microstructures with a gradient in dislocation density, twin fraction, and grain size on the surface of the LPBF samples. The gradient microstructures led to gradient properties and contributed significantly to hetero deformation-induced (HDI) strengthening. Further, a comparison with the wrought counterparts, which showed higher HDI stresses and strain hardening than the LPBF samples, establishes the need for a substantial strength difference between the hard UNSM-affected region and the soft unaffected region for significant HDI strengthening. Moreover, in the current work, a dislocation-based constitutive model is developed to represent the deformation mechanism of the gradient structured sample and is validated with the experimental results.},\n bibtype = {article},\n author = {Karthik, G.M. and Kim, Y. and Kim, E.S. and Zargaran, A. and Sathiyamoorthi, P. and Park, J.M. and Jeong, S.G. and Gu, G.H. and Amanov, A. and Ungar, T. and Kim, H.S.},\n doi = {10.1016/j.addma.2022.103131},\n journal = {Additive Manufacturing}\n}
\n
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\n Developing metal additive parts with a synergy in strength and ductility is a demanding need for many critical applications. Recently, gradient structures have been of research interest as it facilitates intrinsic synergetic strengthening. In the current work, gradient microstructures are obtained on laser-powder bed fusion processed (LPBF) CoCrFeMnNi high entropy alloy using ultrasonic nanocrystal surface modification (UNSM). The UNSM treatment resulted in a thin layer of gradient microstructures with a gradient in dislocation density, twin fraction, and grain size on the surface of the LPBF samples. The gradient microstructures led to gradient properties and contributed significantly to hetero deformation-induced (HDI) strengthening. Further, a comparison with the wrought counterparts, which showed higher HDI stresses and strain hardening than the LPBF samples, establishes the need for a substantial strength difference between the hard UNSM-affected region and the soft unaffected region for significant HDI strengthening. Moreover, in the current work, a dislocation-based constitutive model is developed to represent the deformation mechanism of the gradient structured sample and is validated with the experimental results.\n
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\n  \n 2021\n \n \n (10)\n \n \n
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\n \n\n \n \n \n \n \n TiC-reinforced CoCrFeMnNi composite processed by cold-consolidation and subsequent annealing.\n \n \n \n\n\n \n Asghari-Rad, P.; Nguyen, N.; Kim, Y.; Zargaran, A.; Sathiyamoorthi, P.; and Kim, H.\n\n\n \n\n\n\n Materials Letters, 303. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {TiC-reinforced CoCrFeMnNi composite processed by cold-consolidation and subsequent annealing},\n type = {article},\n year = {2021},\n keywords = {Cold-consolidation,Grain growth,High-entropy alloys,Powder metallurgy},\n volume = {303},\n id = {e02bc785-961e-3869-8cd7-cf513699dcd4},\n created = {2022-09-07T04:57:19.290Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.290Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Nanostructured CoCrFeMnNi high-entropy alloy (HEA) reinforced with TiC nanoparticles was fabricated through cold-consolidation using high-pressure torsion followed by annealing. The microstructural and hardness evolutions of the HEA-TiC composite have been compared with the monolithic HEA sample (without TiC) fabricated by a similar route. The HEA-TiC composite with high densification of 99.5% and uniform distribution of TiC nanoparticles showed retarded grain growth due to the pinning effect and enhanced hardness compared to monolithic HEA. The HPT cold consolidation fabrication route can be utilized to produce various HEA-matrix composites.},\n bibtype = {article},\n author = {Asghari-Rad, P. and Nguyen, N.T.-C. and Kim, Y. and Zargaran, A. and Sathiyamoorthi, P. and Kim, H.S.},\n doi = {10.1016/j.matlet.2021.130503},\n journal = {Materials Letters}\n}
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\n Nanostructured CoCrFeMnNi high-entropy alloy (HEA) reinforced with TiC nanoparticles was fabricated through cold-consolidation using high-pressure torsion followed by annealing. The microstructural and hardness evolutions of the HEA-TiC composite have been compared with the monolithic HEA sample (without TiC) fabricated by a similar route. The HEA-TiC composite with high densification of 99.5% and uniform distribution of TiC nanoparticles showed retarded grain growth due to the pinning effect and enhanced hardness compared to monolithic HEA. The HPT cold consolidation fabrication route can be utilized to produce various HEA-matrix composites.\n
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\n \n\n \n \n \n \n \n Delayed deformation-induced martensite transformation and enhanced cryogenic tensile properties in laser additive manufactured 316L austenitic stainless steel.\n \n \n \n\n\n \n Karthik, G.; Kim, E.; Sathiyamoorthi, P.; Zargaran, A.; Jeong, S.; Xiong, R.; Kang, S.; Cho, J.; and Kim, H.\n\n\n \n\n\n\n Additive Manufacturing, 47. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Delayed deformation-induced martensite transformation and enhanced cryogenic tensile properties in laser additive manufactured 316L austenitic stainless steel},\n type = {article},\n year = {2021},\n keywords = {Cryogenic properties,Direct energy deposition,Selective laser melting,Stainless steel,Transformation induced plasticity},\n volume = {47},\n id = {63dc4004-7825-3484-ac07-96927dbf398d},\n created = {2022-09-07T04:57:19.352Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.352Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The cellular dislocation structure is an important microstructure aspect in fusion-based laser metal additive manufactured (MAM) parts. Its role in increasing strength and ductility at room temperature (298 K) is a known phenomenon. In this work, we have shown that the cellular dislocation structure not only improves the strength but also dramatically increases the mechanical stability of the austenite and retards the deformation-induced martensite transformation (DIMT) of austenite at cryogenic temperature (77 K). The delayed and slow rate of DIMT led to an enhanced strength-ductility synergy in the direct energy deposited and selective laser melted 316 L stainless steel samples at 77 K compared to the wrought processed samples. The current study establishes the capability of MAM technologies in controlling the DIMT behavior and realizing materials with high strength and ductility combination.},\n bibtype = {article},\n author = {Karthik, G.M. and Kim, E.S. and Sathiyamoorthi, P. and Zargaran, A. and Jeong, S.G. and Xiong, R. and Kang, S.H. and Cho, J.-W. and Kim, H.S.},\n doi = {10.1016/j.addma.2021.102314},\n journal = {Additive Manufacturing}\n}
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\n The cellular dislocation structure is an important microstructure aspect in fusion-based laser metal additive manufactured (MAM) parts. Its role in increasing strength and ductility at room temperature (298 K) is a known phenomenon. In this work, we have shown that the cellular dislocation structure not only improves the strength but also dramatically increases the mechanical stability of the austenite and retards the deformation-induced martensite transformation (DIMT) of austenite at cryogenic temperature (77 K). The delayed and slow rate of DIMT led to an enhanced strength-ductility synergy in the direct energy deposited and selective laser melted 316 L stainless steel samples at 77 K compared to the wrought processed samples. The current study establishes the capability of MAM technologies in controlling the DIMT behavior and realizing materials with high strength and ductility combination.\n
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\n \n\n \n \n \n \n \n Effect of heat treatment on microstructural heterogeneity and mechanical properties of 1%C-CoCrFeMnNi alloy fabricated by selective laser melting.\n \n \n \n\n\n \n Park, J.; Kim, E.; Kwon, H.; Sathiyamoorthi, P.; Kim, K.; Yu, J.; and Kim, H.\n\n\n \n\n\n\n Additive Manufacturing, 47. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Effect of heat treatment on microstructural heterogeneity and mechanical properties of 1%C-CoCrFeMnNi alloy fabricated by selective laser melting},\n type = {article},\n year = {2021},\n keywords = {Heat treatment,High-entropy alloy,Mechanical properties,Microstructural heterogeneity,Selective laser melting},\n volume = {47},\n id = {4b76533c-20c3-3377-b881-cdbfff81f64e},\n created = {2022-09-07T04:57:19.361Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.361Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In this study, we quantitatively investigated the effect of heat treatment on microstructural evolution and mechanical properties in the selective laser melting (SLM) processed 1%C-CoCrFeMnNi high-entropy alloy (C-HEA). The addition of carbon atoms resulted in a nano-sized Cr23C6 carbide phase in the SLM-processed C-HEA, significantly retarding the kinetics of recrystallization and grain growth during the annealing heat treatment. The volume fraction of the carbide in SLM-processed C-HEA increased from ~1.7 vol% to ~2.9 vol% after exposure to the annealing heat treatment in the temperature range of Cr-rich carbide formation. After annealing, the combination of ultimate tensile strength and uniform elongation is improved with enhanced strain hardening ability. The increased volume fraction of finely distributed nano-carbides at cell boundaries in the annealed C-HEA can effectively generate high back stress by profuse geometrically necessary dislocations (GNDs) during plastic deformation. This work demonstrates that the heat treatment of the SLM-processed C-HEAs is an attractive method to enhance mechanical properties and the reliability of product quality used in high-tech applications. This work also provides theoretical support to beneficially control the microstructural heterogeneity in the SLM-processed alloys to obtain the desired performance in structural parts.},\n bibtype = {article},\n author = {Park, J.M. and Kim, E.S. and Kwon, H. and Sathiyamoorthi, P. and Kim, K.T. and Yu, J.-H. and Kim, H.S.},\n doi = {10.1016/j.addma.2021.102283},\n journal = {Additive Manufacturing}\n}
\n
\n\n\n
\n In this study, we quantitatively investigated the effect of heat treatment on microstructural evolution and mechanical properties in the selective laser melting (SLM) processed 1%C-CoCrFeMnNi high-entropy alloy (C-HEA). The addition of carbon atoms resulted in a nano-sized Cr23C6 carbide phase in the SLM-processed C-HEA, significantly retarding the kinetics of recrystallization and grain growth during the annealing heat treatment. The volume fraction of the carbide in SLM-processed C-HEA increased from ~1.7 vol% to ~2.9 vol% after exposure to the annealing heat treatment in the temperature range of Cr-rich carbide formation. After annealing, the combination of ultimate tensile strength and uniform elongation is improved with enhanced strain hardening ability. The increased volume fraction of finely distributed nano-carbides at cell boundaries in the annealed C-HEA can effectively generate high back stress by profuse geometrically necessary dislocations (GNDs) during plastic deformation. This work demonstrates that the heat treatment of the SLM-processed C-HEAs is an attractive method to enhance mechanical properties and the reliability of product quality used in high-tech applications. This work also provides theoretical support to beneficially control the microstructural heterogeneity in the SLM-processed alloys to obtain the desired performance in structural parts.\n
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\n \n\n \n \n \n \n \n 2.3 GPa cryogenic strength through thermal-induced and deformation-induced body-centered cubic martensite in a novel ferrous medium entropy alloy.\n \n \n \n\n\n \n Kwon, H.; Sathiyamoorthi, P.; Karthik, G.; Asghari-Rad, P.; Zargaran, A.; Do, H.; Lee, B.; Kato, H.; and Kim, H.\n\n\n \n\n\n\n Scripta Materialia, 204. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {2.3 GPa cryogenic strength through thermal-induced and deformation-induced body-centered cubic martensite in a novel ferrous medium entropy alloy},\n type = {article},\n year = {2021},\n keywords = {Dislocation structure,Maraging medium-entropy alloys,Martensitic phase transformation,Plastic deformation,Work hardening},\n volume = {204},\n id = {2cc48d4d-b805-32af-ab31-85c8718324f5},\n created = {2022-09-07T04:57:19.425Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.425Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A novel non-equiatomic FeCoNiAlTiMo ferrous medium-entropy alloy (MEA) with ultra-high tensile strengths at 298 and 77 K is presented in this work. By subjecting the MEA to hot rolling without further heat treatment, a quasi-dual-phase microstructure consisting of retained face-centered cubic (FCC) and thermal body-centered cubic martensite (BCC) phases with a very high density of dislocations and precipitates of Mo-rich µ phase was created. The high dislocation density significantly accelerated deformation-induced martensitic transformation from the remaining metastable FCC to BCC and successfully increased strain hardening ability. The strain hardening ability was even higher at 77 K due to decreasing FCC phase stability at lower temperatures. The increased strain hardening ability led to an excellent balance of strength and ductility, with ultimate tensile strength/uniform elongation of ~1.5 GPa/~15% at 298 K and ~2.3 GPa/~11% at 77 K.},\n bibtype = {article},\n author = {Kwon, H. and Sathiyamoorthi, P. and Karthik, G.M. and Asghari-Rad, P. and Zargaran, A. and Do, H.-S. and Lee, B.-J. and Kato, H. and Kim, H.S.},\n doi = {10.1016/j.scriptamat.2021.114157},\n journal = {Scripta Materialia}\n}
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\n A novel non-equiatomic FeCoNiAlTiMo ferrous medium-entropy alloy (MEA) with ultra-high tensile strengths at 298 and 77 K is presented in this work. By subjecting the MEA to hot rolling without further heat treatment, a quasi-dual-phase microstructure consisting of retained face-centered cubic (FCC) and thermal body-centered cubic martensite (BCC) phases with a very high density of dislocations and precipitates of Mo-rich µ phase was created. The high dislocation density significantly accelerated deformation-induced martensitic transformation from the remaining metastable FCC to BCC and successfully increased strain hardening ability. The strain hardening ability was even higher at 77 K due to decreasing FCC phase stability at lower temperatures. The increased strain hardening ability led to an excellent balance of strength and ductility, with ultimate tensile strength/uniform elongation of ~1.5 GPa/~15% at 298 K and ~2.3 GPa/~11% at 77 K.\n
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\n \n\n \n \n \n \n \n Nanocrystalline High Entropy Alloys: Processing and Properties.\n \n \n \n\n\n \n Sathiyamoorthi, P.; and Kim, H.\n\n\n \n\n\n\n 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
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@book{\n title = {Nanocrystalline High Entropy Alloys: Processing and Properties},\n type = {book},\n year = {2021},\n source = {Encyclopedia of Materials: Metals and Alloys},\n id = {cb1921f1-140f-37cf-af25-11369ca048b4},\n created = {2022-09-07T04:57:19.431Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.431Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n bibtype = {book},\n author = {Sathiyamoorthi, P. and Kim, H.S.},\n doi = {10.1016/B978-0-12-803581-8.11720-5}\n}
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\n \n\n \n \n \n \n \n Synergetic strengthening from grain refinement and nano-scale precipitates in non-equiatomic CoCrFeNiMo medium-entropy alloy.\n \n \n \n\n\n \n Kwon, H.; Asghari-Rad, P.; Park, J.; Sathiyamoorthi, P.; Bae, J.; Moon, J.; Zargaran, A.; Choi, Y.; Son, S.; and Kim, H.\n\n\n \n\n\n\n Intermetallics, 135. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Synergetic strengthening from grain refinement and nano-scale precipitates in non-equiatomic CoCrFeNiMo medium-entropy alloy},\n type = {article},\n year = {2021},\n keywords = {High-entropy alloy,Mechanical properties,Nanocrystalline structure,Nucleation and growth,Severe plastic deformation},\n volume = {135},\n id = {4cd4292f-8d5d-3036-a262-fe7b64ee94b5},\n created = {2022-09-07T04:57:19.491Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.491Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A strategy to improve the tensile properties of Co17.5Cr12.5Fe55Ni10Mo5 (at%) medium-entropy alloy through high-pressure torsion and subsequent annealing is presented in this work. Microstructural study revealed that the high-pressure torsion process led to the formation of fine grains (≤~1 μm) and profuse nano-scale Mo-rich μ-phase precipitates. And resultantly, the yield strength of the alloy was tuned from ~400 MPa to ~1 GPa, while preserving reasonable uniform elongation over 15%. The combination of strengthening from grain refinement and precipitation contributed to the excellent strength, while the post-HPT annealing provided substantial ductility.},\n bibtype = {article},\n author = {Kwon, H. and Asghari-Rad, P. and Park, J.M. and Sathiyamoorthi, P. and Bae, J.W. and Moon, J. and Zargaran, A. and Choi, Y.T. and Son, S. and Kim, H.S.},\n doi = {10.1016/j.intermet.2021.107212},\n journal = {Intermetallics}\n}
\n
\n\n\n
\n A strategy to improve the tensile properties of Co17.5Cr12.5Fe55Ni10Mo5 (at%) medium-entropy alloy through high-pressure torsion and subsequent annealing is presented in this work. Microstructural study revealed that the high-pressure torsion process led to the formation of fine grains (≤~1 μm) and profuse nano-scale Mo-rich μ-phase precipitates. And resultantly, the yield strength of the alloy was tuned from ~400 MPa to ~1 GPa, while preserving reasonable uniform elongation over 15%. The combination of strengthening from grain refinement and precipitation contributed to the excellent strength, while the post-HPT annealing provided substantial ductility.\n
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\n \n\n \n \n \n \n \n Architectured multi-metal CoCrFeMnNi-Inconel 718 lamellar composite by high-pressure torsion.\n \n \n \n\n\n \n Karthik, G.; Asghari-Rad, P.; Sathiyamoorthi, P.; Zargaran, A.; Kim, E.; Kim, T.; and Kim, H.\n\n\n \n\n\n\n Scripta Materialia, 195. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
\n
@article{\n title = {Architectured multi-metal CoCrFeMnNi-Inconel 718 lamellar composite by high-pressure torsion},\n type = {article},\n year = {2021},\n keywords = {Composites,High entropy alloy,High-pressure torsion,Multi-materials,Powder metallurgy},\n volume = {195},\n id = {4721c93f-c554-3dcb-bb45-af9d62fb57dc},\n created = {2022-09-07T04:57:19.497Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.497Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Multi-metal composites have gained much interest in recent years to explore the unfilled space of the strength-elongation window. However, producing these composites is challenging and is limited to a few material combinations because most processing techniques involve melting/solidification and high-temperatures. This work demonstrates a new powder metallurgy-based approach to produce these composites using high-pressure torsion. Lamellar nano-crystalline composite with high entropy alloy (CoCrFeMnFe) matrix and uniformly distributed nickel-base superalloy (Inconel 718) reinforcement are realized after high-pressure torsion. The current approach has resulted in an excellent metallurgical bonded interface with an ultra-fine grain size in both the matrix and reinforcement. The samples showed an exceptional synergy of high yield strength ~900 MPa and elongation ~40%, overcoming the perennial challenge in multi-metal composites. The current approach is versatile and can open up a horizon of multi-material combinations with a synergy of strength and ductility.},\n bibtype = {article},\n author = {Karthik, G.M. and Asghari-Rad, P. and Sathiyamoorthi, P. and Zargaran, A. and Kim, E.S. and Kim, T.S. and Kim, H.S.},\n doi = {10.1016/j.scriptamat.2021.113722},\n journal = {Scripta Materialia}\n}
\n
\n\n\n
\n Multi-metal composites have gained much interest in recent years to explore the unfilled space of the strength-elongation window. However, producing these composites is challenging and is limited to a few material combinations because most processing techniques involve melting/solidification and high-temperatures. This work demonstrates a new powder metallurgy-based approach to produce these composites using high-pressure torsion. Lamellar nano-crystalline composite with high entropy alloy (CoCrFeMnFe) matrix and uniformly distributed nickel-base superalloy (Inconel 718) reinforcement are realized after high-pressure torsion. The current approach has resulted in an excellent metallurgical bonded interface with an ultra-fine grain size in both the matrix and reinforcement. The samples showed an exceptional synergy of high yield strength ~900 MPa and elongation ~40%, overcoming the perennial challenge in multi-metal composites. The current approach is versatile and can open up a horizon of multi-material combinations with a synergy of strength and ductility.\n
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\n \n\n \n \n \n \n \n Unusual strain-induced martensite and absence of conventional grain refinement in twinning induced plasticity high-entropy alloy processed by high-pressure torsion.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Asghari-Rad, P.; Karthik, G.; Zargaran, A.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 803. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
\n
@article{\n title = {Unusual strain-induced martensite and absence of conventional grain refinement in twinning induced plasticity high-entropy alloy processed by high-pressure torsion},\n type = {article},\n year = {2021},\n keywords = {High-entropy alloys,High-pressure torsion,Martensitic transformation,Sigma phase,Transformation induced plasticity},\n volume = {803},\n id = {b7c4b3b4-21cf-3218-bf2d-43f43a182176},\n created = {2022-09-07T04:57:19.552Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.552Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A Fe40Mn40Co10Cr10 twinning induced plasticity high-entropy alloy was processed by high-pressure torsion, and its microstructure and mechanical properties were studied. The results indicate the absence of typical grain refinement, but rather the original grain size was retained with the formation of strain-induced HCP martensitic phase.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Asghari-Rad, P. and Karthik, G.M. and Zargaran, A. and Kim, H.S.},\n doi = {10.1016/j.msea.2020.140570},\n journal = {Materials Science and Engineering A}\n}
\n
\n\n\n
\n A Fe40Mn40Co10Cr10 twinning induced plasticity high-entropy alloy was processed by high-pressure torsion, and its microstructure and mechanical properties were studied. The results indicate the absence of typical grain refinement, but rather the original grain size was retained with the formation of strain-induced HCP martensitic phase.\n
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\n \n\n \n \n \n \n \n Superplastic Behavior in High-Pressure Torsion-Processed Mo7.5Fe55Co18Cr12.5Ni7 Medium-Entropy Alloy.\n \n \n \n\n\n \n Nguyen, N.; Asghari-Rad, P.; Bae, J.; Sathiyamoorthi, P.; and Kim, H.\n\n\n \n\n\n\n Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 52(1). 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n
@article{\n title = {Superplastic Behavior in High-Pressure Torsion-Processed Mo<inf>7.5</inf>Fe<inf>55</inf>Co<inf>18</inf>Cr<inf>12.5</inf>Ni<inf>7</inf> Medium-Entropy Alloy},\n type = {article},\n year = {2021},\n volume = {52},\n id = {44123795-92b7-3e22-a5cc-e620bda25b6c},\n created = {2022-09-07T04:57:19.559Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.559Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the present study, superplasticity of high-pressure torsion-processed non-equiatomic Mo7.5Co18Cr12.5Fe55Ni7 medium-entropy alloy with nanograins was investigated. The superplastic elongation of 505 pct was achieved at a temperature of 800 °C and a low strain rate. The precipitation of the μ phase enriched with Mo hinders the grain boundary migration and also acts as the origin for cavity and crack formation.},\n bibtype = {article},\n author = {Nguyen, N.T.-C. and Asghari-Rad, P. and Bae, J.W. and Sathiyamoorthi, P. and Kim, H.S.},\n doi = {10.1007/s11661-020-06033-3},\n journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},\n number = {1}\n}
\n
\n\n\n
\n In the present study, superplasticity of high-pressure torsion-processed non-equiatomic Mo7.5Co18Cr12.5Fe55Ni7 medium-entropy alloy with nanograins was investigated. The superplastic elongation of 505 pct was achieved at a temperature of 800 °C and a low strain rate. The precipitation of the μ phase enriched with Mo hinders the grain boundary migration and also acts as the origin for cavity and crack formation.\n
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\n \n\n \n \n \n \n \n A powder-metallurgy-based fabrication route towards achieving high tensile strength with ultra-high ductility in high-entropy alloy.\n \n \n \n\n\n \n Asghari-Rad, P.; Sathiyamoorthi, P.; Nguyen, N.; Zargaran, A.; Kim, T.; and Kim, H.\n\n\n \n\n\n\n Scripta Materialia, 190. 2021.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {A powder-metallurgy-based fabrication route towards achieving high tensile strength with ultra-high ductility in high-entropy alloy},\n type = {article},\n year = {2021},\n keywords = {Cold-consolidation,High-entropy alloy,High-pressure torsion,Mechanical properties,Powder metallurgy},\n volume = {190},\n id = {955f963f-cfed-3a61-bebc-8d2efe919971},\n created = {2022-09-07T04:57:19.616Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.616Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The strength-ductility trade-off dilemma is perennially problematic in the materials science community. In particular, the attainability of high tensile strength and large elongation is ambitious in alloys fabricated by powder metallurgy. Here, we demonstrate a powder-metallurgy-based fabrication route to achieve a high synergy of tensile strength and ductility through cold-consolidation of CoCrFeMnNi high-entropy alloy powder using high-pressure torsion followed by annealing. This approach has resulted in an exceptional synergy of high yield strength of 754 MPa with an ultra-high tensile elongation of 58%% which has never been achieved in alloys fabricated by powder metallurgy routes. Additionally, the microstructure can be tuned by annealing treatment to achieve a range of strength and ductility that are highly sought after in industries for a specific application. The present fabrication route can be applied for fabrication of high-entropy alloy-matrix composites using alloys, metals, and ceramic powders to achieve controllable microstructure and eminent tensile properties.},\n bibtype = {article},\n author = {Asghari-Rad, P. and Sathiyamoorthi, P. and Nguyen, N.T.-C. and Zargaran, A. and Kim, T.S. and Kim, H.S.},\n doi = {10.1016/j.scriptamat.2020.08.038},\n journal = {Scripta Materialia}\n}
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\n The strength-ductility trade-off dilemma is perennially problematic in the materials science community. In particular, the attainability of high tensile strength and large elongation is ambitious in alloys fabricated by powder metallurgy. Here, we demonstrate a powder-metallurgy-based fabrication route to achieve a high synergy of tensile strength and ductility through cold-consolidation of CoCrFeMnNi high-entropy alloy powder using high-pressure torsion followed by annealing. This approach has resulted in an exceptional synergy of high yield strength of 754 MPa with an ultra-high tensile elongation of 58%% which has never been achieved in alloys fabricated by powder metallurgy routes. Additionally, the microstructure can be tuned by annealing treatment to achieve a range of strength and ductility that are highly sought after in industries for a specific application. The present fabrication route can be applied for fabrication of high-entropy alloy-matrix composites using alloys, metals, and ceramic powders to achieve controllable microstructure and eminent tensile properties.\n
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\n  \n 2020\n \n \n (5)\n \n \n
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\n \n\n \n \n \n \n \n Ultrahigh high-strain-rate superplasticity in a nanostructured high-entropy alloy.\n \n \n \n\n\n \n Nguyen, N.; Asghari-Rad, P.; Sathiyamoorthi, P.; Zargaran, A.; Lee, C.; and Kim, H.\n\n\n \n\n\n\n Nature Communications, 11(1). 2020.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n
@article{\n title = {Ultrahigh high-strain-rate superplasticity in a nanostructured high-entropy alloy},\n type = {article},\n year = {2020},\n volume = {11},\n id = {e51c93b6-8f43-36d4-934e-e77a4dd05307},\n created = {2022-09-07T04:57:19.619Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.619Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Superplasticity describes a material’s ability to sustain large plastic deformation in the form of a tensile elongation to over 400% of its original length, but is generally observed only at a low strain rate (~10−4 s−1), which results in long processing times that are economically undesirable for mass production. Superplasticity at high strain rates in excess of 10−2 s−1, required for viable industry-scale application, has usually only been achieved in low-strength aluminium and magnesium alloys. Here, we present a superplastic elongation to 2000% of the original length at a high strain rate of 5 × 10−2 s−1 in an Al9(CoCrFeMnNi)91 (at%) high-entropy alloy nanostructured using high-pressure torsion. The high-pressure torsion induced grain refinement in the multi-phase alloy combined with limited grain growth during hot plastic deformation enables high strain rate superplasticity through grain boundary sliding accommodated by dislocation activity.},\n bibtype = {article},\n author = {Nguyen, N.T.-C. and Asghari-Rad, P. and Sathiyamoorthi, P. and Zargaran, A. and Lee, C.S. and Kim, H.S.},\n doi = {10.1038/s41467-020-16601-1},\n journal = {Nature Communications},\n number = {1}\n}
\n
\n\n\n
\n Superplasticity describes a material’s ability to sustain large plastic deformation in the form of a tensile elongation to over 400% of its original length, but is generally observed only at a low strain rate (~10−4 s−1), which results in long processing times that are economically undesirable for mass production. Superplasticity at high strain rates in excess of 10−2 s−1, required for viable industry-scale application, has usually only been achieved in low-strength aluminium and magnesium alloys. Here, we present a superplastic elongation to 2000% of the original length at a high strain rate of 5 × 10−2 s−1 in an Al9(CoCrFeMnNi)91 (at%) high-entropy alloy nanostructured using high-pressure torsion. The high-pressure torsion induced grain refinement in the multi-phase alloy combined with limited grain growth during hot plastic deformation enables high strain rate superplasticity through grain boundary sliding accommodated by dislocation activity.\n
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\n \n\n \n \n \n \n \n Novel precipitation and enhanced tensile properties in selective laser melted Cu-Sn alloy.\n \n \n \n\n\n \n Karthik, G.; Sathiyamoorthi, P.; Zargaran, A.; Park, J.; Asghari-Rad, P.; Son, S.; Park, S.; and Kim, H.\n\n\n \n\n\n\n Materialia, 13. 2020.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Novel precipitation and enhanced tensile properties in selective laser melted Cu-Sn alloy},\n type = {article},\n year = {2020},\n keywords = {Cu-Sn alloy,Heterogeneous microstructure,Laser powder-bed fusion,Mechanical anisotropy,Selective laser melting},\n volume = {13},\n id = {d2617911-c9df-39af-b47f-154155d5fe5e},\n created = {2022-09-07T04:57:19.674Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.674Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The current work reports nano-precipitation and exceptional combination of high strength and ductility in a Cu-13Sn alloy, fabricated by selective laser melting (SLM). The SLM samples revealed competitive unidirectional columnar grains with a fine cellular structure (~600 nm) having Cu-rich spherical nano-precipitates (~3 nm), and δ-phase (Cu41Sn11). Besides, the SLM samples presented a spatially heterogeneous microstructure with both microstructural and chemical heterogeneities in the length scales ranging from micron to nano-scale. The microstructural heterogeneity arises from the heterogeneous grain structure (alternate layers of coarse and fine grains) and dislocation density variations (regions with high and low fractions of low-angle boundaries). Further, the chemical heterogeneity is from the segregation of Sn to the cellular boundaries. The multi-phase hierarchy and spatially heterogeneous microstructure with fine cellular structure significantly contributed to an exceptional combination of high strength and ductility in three orthogonal directions of the SLM processed Cu-13Sn alloy. The back stress due to the heterogeneous structure and the effective stress due to the nano-precipitates, fine grains, and friction stress contribute to realizing exceptional strength. The presence of cellular structure and geometrically necessary dislocations contribute to achieving high uniform elongation in the SLM processed Cu-13Sn alloy. Overall, this work demonstrates the capability of the SLM process in developing novel heterogeneous materials with minimum tensile anisotropy and an exceptional combination of high strength and ductility.},\n bibtype = {article},\n author = {Karthik, G.M. and Sathiyamoorthi, P. and Zargaran, A. and Park, J.M. and Asghari-Rad, P. and Son, S. and Park, S.H. and Kim, H.S.},\n doi = {10.1016/j.mtla.2020.100861},\n journal = {Materialia}\n}
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\n The current work reports nano-precipitation and exceptional combination of high strength and ductility in a Cu-13Sn alloy, fabricated by selective laser melting (SLM). The SLM samples revealed competitive unidirectional columnar grains with a fine cellular structure (~600 nm) having Cu-rich spherical nano-precipitates (~3 nm), and δ-phase (Cu41Sn11). Besides, the SLM samples presented a spatially heterogeneous microstructure with both microstructural and chemical heterogeneities in the length scales ranging from micron to nano-scale. The microstructural heterogeneity arises from the heterogeneous grain structure (alternate layers of coarse and fine grains) and dislocation density variations (regions with high and low fractions of low-angle boundaries). Further, the chemical heterogeneity is from the segregation of Sn to the cellular boundaries. The multi-phase hierarchy and spatially heterogeneous microstructure with fine cellular structure significantly contributed to an exceptional combination of high strength and ductility in three orthogonal directions of the SLM processed Cu-13Sn alloy. The back stress due to the heterogeneous structure and the effective stress due to the nano-precipitates, fine grains, and friction stress contribute to realizing exceptional strength. The presence of cellular structure and geometrically necessary dislocations contribute to achieving high uniform elongation in the SLM processed Cu-13Sn alloy. Overall, this work demonstrates the capability of the SLM process in developing novel heterogeneous materials with minimum tensile anisotropy and an exceptional combination of high strength and ductility.\n
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\n \n\n \n \n \n \n \n A Powder-Metallurgy-Based Fabrication Route towards Achieving High Tensile Strength with Ultra-High Ductility in High-Entropy Alloy.\n \n \n \n\n\n \n Asghari-Rad, P.; Sathiyamoorthi, P.; Nguyen, N.; Zargaran, A.; Kim, T.; and Kim, H.\n\n\n \n\n\n\n 2020.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@misc{\n title = {A Powder-Metallurgy-Based Fabrication Route towards Achieving High Tensile Strength with Ultra-High Ductility in High-Entropy Alloy},\n type = {misc},\n year = {2020},\n source = {SSRN},\n keywords = {Cold-consolidation,High-entropy alloy,High-pressure torsion,Mechanical properties,Powder metallurgy},\n id = {d483d91a-2f31-3371-a919-00d7246324c3},\n created = {2022-09-07T04:57:19.679Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.679Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The strength-ductility trade-off dilemma is perennially problematic in the materials science community. In particular, the attainability of high tensile strength and large elongation is ambitious on alloys fabricated by powder metallurgy. Here we demonstrate a powder-metallurgy-based fabrication route to achieve high synergy of tensile strength and ductility through cold-consolidation of CoCrFeMnNi high-entropy alloy powder using high-pressure torsion followed by annealing. This approach has resulted in an exceptional synergy of high yield strength of 754 MPa with an ultra-high tensile elongation of 58% that has never been achieved in alloys fabricated by powder metallurgy routes. Additionally, the microstructure can be tuned by annealing treatment to achieve a range of strength and ductility that are highly sought after in industries for a specific application. The present fabrication route can be applied to fabricate high-entropy alloy-matrix composites using alloys, metals, and ceramic powders leading to a controllable microstructure and eminent tensile properties.},\n bibtype = {misc},\n author = {Asghari-Rad, P. and Sathiyamoorthi, P. and Nguyen, N.T.-C. and Zargaran, A. and Kim, T.S. and Kim, H.S.},\n doi = {10.2139/ssrn.3659824}\n}
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\n The strength-ductility trade-off dilemma is perennially problematic in the materials science community. In particular, the attainability of high tensile strength and large elongation is ambitious on alloys fabricated by powder metallurgy. Here we demonstrate a powder-metallurgy-based fabrication route to achieve high synergy of tensile strength and ductility through cold-consolidation of CoCrFeMnNi high-entropy alloy powder using high-pressure torsion followed by annealing. This approach has resulted in an exceptional synergy of high yield strength of 754 MPa with an ultra-high tensile elongation of 58% that has never been achieved in alloys fabricated by powder metallurgy routes. Additionally, the microstructure can be tuned by annealing treatment to achieve a range of strength and ductility that are highly sought after in industries for a specific application. The present fabrication route can be applied to fabricate high-entropy alloy-matrix composites using alloys, metals, and ceramic powders leading to a controllable microstructure and eminent tensile properties.\n
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\n \n\n \n \n \n \n \n Fine-tuning of mechanical properties in V10Cr15Mn5Fe35Co10Ni25 high-entropy alloy through high-pressure torsion and annealing.\n \n \n \n\n\n \n Asghari-Rad, P.; Sathiyamoorthi, P.; Thi-Cam Nguyen, N.; Bae, J.; Shahmir, H.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 771. 2020.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Fine-tuning of mechanical properties in V<inf>10</inf>Cr<inf>15</inf>Mn<inf>5</inf>Fe<inf>35</inf>Co<inf>10</inf>Ni<inf>25</inf> high-entropy alloy through high-pressure torsion and annealing},\n type = {article},\n year = {2020},\n keywords = {Grain refinement,High-entropy alloy,High-pressure torsion,Post-deformation annealing,Strengthening mechanisms,Thermo-mechanical processing},\n volume = {771},\n id = {dbd883cb-cf37-3907-97b6-e43fc50308b4},\n created = {2022-09-07T04:57:19.753Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.753Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy (HEA) was subjected to high-pressure torsion (HPT) and subsequently annealed under different conditions to study its microstructural evolution and mechanical properties. The HPT-processed sample consisted of a nanocrystalline structure with an average grain size of 30 nm. Annealing at 600 °C for 2 min led to annealing induced hardening because of the formation of sigma phase, whereas samples annealed at higher temperatures showed a monotonous decrease in hardness because of dislocation recovery and grain growth. The average number of geometrically necessary dislocations decreased with increase in the temperature and duration time, indicating recovery of HPT-induced dislocations. Tensile properties indicated that the yield strength and ductility are notably influenced by the microstructure after annealing. The post-HPT annealing at 700 °C for 10 min resulted in an outstanding synergy of high tensile strength (~1.54 GPa) and good elongation-to-failure (~11%).},\n bibtype = {article},\n author = {Asghari-Rad, P. and Sathiyamoorthi, P. and Thi-Cam Nguyen, N. and Bae, J.W. and Shahmir, H. and Kim, H.S.},\n doi = {10.1016/j.msea.2019.138604},\n journal = {Materials Science and Engineering A}\n}
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\n\n\n
\n A V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy (HEA) was subjected to high-pressure torsion (HPT) and subsequently annealed under different conditions to study its microstructural evolution and mechanical properties. The HPT-processed sample consisted of a nanocrystalline structure with an average grain size of 30 nm. Annealing at 600 °C for 2 min led to annealing induced hardening because of the formation of sigma phase, whereas samples annealed at higher temperatures showed a monotonous decrease in hardness because of dislocation recovery and grain growth. The average number of geometrically necessary dislocations decreased with increase in the temperature and duration time, indicating recovery of HPT-induced dislocations. Tensile properties indicated that the yield strength and ductility are notably influenced by the microstructure after annealing. The post-HPT annealing at 700 °C for 10 min resulted in an outstanding synergy of high tensile strength (~1.54 GPa) and good elongation-to-failure (~11%).\n
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\n \n\n \n \n \n \n \n Effect of Initial Grain Size on Deformation Mechanism during High-Pressure Torsion in V10Cr15Mn5Fe35Co10Ni25 High-Entropy Alloy.\n \n \n \n\n\n \n Asghari-Rad, P.; Sathiyamoorthi, P.; Bae, J.; Shahmir, H.; Zargaran, A.; and Kim, H.\n\n\n \n\n\n\n Advanced Engineering Materials, 22(1). 2020.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Effect of Initial Grain Size on Deformation Mechanism during High-Pressure Torsion in V<inf>10</inf>Cr<inf>15</inf>Mn<inf>5</inf>Fe<inf>35</inf>Co<inf>10</inf>Ni<inf>25</inf> High-Entropy Alloy},\n type = {article},\n year = {2020},\n keywords = {deformation mechanism,high-entropy alloys,high-pressure torsion,mechanical twinning,nano-grained materials},\n volume = {22},\n id = {0bffc758-c269-3af6-937e-f94c221d17d6},\n created = {2022-09-07T04:57:19.758Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.758Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The transition of the deformation mechanism from the dislocation slip-mediated mechanism to the twin-mediated mechanism with increasing grain size is a well-observed phenomenon in materials with low stacking fault energy during compression/tensile tests. To understand this effect further at large strains, a V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy with two initial average grain sizes is processed by high-pressure torsion (HPT) at different numbers of turns. The results indicate that initial grain size plays a significant role in the deformation mechanism during the HPT process. The fine-grained (FG) sample exhibits only a tangled dislocation structure, whereas mechanical twins are observed along with the formation of dislocations in the coarse-grained (CG) sample after the one-fourth turn. High dislocation density is observed in the CG sample after the one-fourth and first turn, which leads to a higher rate of hardness increment as compared with the FG sample. However, a similar microstructure and mechanical properties are observed after five turns of HPT processing in both FG and CG samples. After five turns, the microstructure consists of nanograins (average grain size ≈30 nm) with nanotwins, and the samples exhibit a very high ultimate tensile strength of ≈2 GPa with a reasonable elongation to failure of ≈6%.},\n bibtype = {article},\n author = {Asghari-Rad, P. and Sathiyamoorthi, P. and Bae, J.W. and Shahmir, H. and Zargaran, A. and Kim, H.S.},\n doi = {10.1002/adem.201900587},\n journal = {Advanced Engineering Materials},\n number = {1}\n}
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\n The transition of the deformation mechanism from the dislocation slip-mediated mechanism to the twin-mediated mechanism with increasing grain size is a well-observed phenomenon in materials with low stacking fault energy during compression/tensile tests. To understand this effect further at large strains, a V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy with two initial average grain sizes is processed by high-pressure torsion (HPT) at different numbers of turns. The results indicate that initial grain size plays a significant role in the deformation mechanism during the HPT process. The fine-grained (FG) sample exhibits only a tangled dislocation structure, whereas mechanical twins are observed along with the formation of dislocations in the coarse-grained (CG) sample after the one-fourth turn. High dislocation density is observed in the CG sample after the one-fourth and first turn, which leads to a higher rate of hardness increment as compared with the FG sample. However, a similar microstructure and mechanical properties are observed after five turns of HPT processing in both FG and CG samples. After five turns, the microstructure consists of nanograins (average grain size ≈30 nm) with nanotwins, and the samples exhibit a very high ultimate tensile strength of ≈2 GPa with a reasonable elongation to failure of ≈6%.\n
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\n  \n 2019\n \n \n (8)\n \n \n
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\n \n\n \n \n \n \n \n Achieving high strength and high ductility in Al0.3CoCrNi medium-entropy alloy through multi-phase hierarchical microstructure.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Park, J.; Moon, J.; Bae, J.; Asghari-Rad, P.; Zargaran, A.; and Seop Kim, H.\n\n\n \n\n\n\n Materialia, 8. 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Achieving high strength and high ductility in Al<inf>0.3</inf>CoCrNi medium-entropy alloy through multi-phase hierarchical microstructure},\n type = {article},\n year = {2019},\n keywords = {Back stress,Bimodal grain size,Deformation twinning,Heterogeneous microstructure,Precipitates},\n volume = {8},\n id = {22a70052-97cf-39b9-8a13-241d2338d3a0},\n created = {2022-09-07T04:57:19.887Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.887Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The enhancement of strength in materials by conventional strengthening mechanism is always accompanied by loss of ductility due to the reduced strain hardenability, leading to a strength–ductility trade-off. In this paper, we engineered Al0.3CoCrNi medium-entropy alloy to contain multi-phase hierarchical microstructure and demonstrated a high yield strength of ∼1 GPa, a high tensile strength of ∼1.2 GPa, with a uniform elongation and total elongation of ∼28% and ∼39%, respectively. The multi-phase hierarchical microstructure is developed by a simple processing route of cold rolling followed by annealing. The superior combination of strength and ductility is primarily attributed to the generation of back stress, high strain hardening rate, and formation of deformation twins.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Park, J.M. and Moon, J. and Bae, J.W. and Asghari-Rad, P. and Zargaran, A. and Seop Kim, H.},\n doi = {10.1016/j.mtla.2019.100442},\n journal = {Materialia}\n}
\n
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\n The enhancement of strength in materials by conventional strengthening mechanism is always accompanied by loss of ductility due to the reduced strain hardenability, leading to a strength–ductility trade-off. In this paper, we engineered Al0.3CoCrNi medium-entropy alloy to contain multi-phase hierarchical microstructure and demonstrated a high yield strength of ∼1 GPa, a high tensile strength of ∼1.2 GPa, with a uniform elongation and total elongation of ∼28% and ∼39%, respectively. The multi-phase hierarchical microstructure is developed by a simple processing route of cold rolling followed by annealing. The superior combination of strength and ductility is primarily attributed to the generation of back stress, high strain hardening rate, and formation of deformation twins.\n
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\n \n\n \n \n \n \n \n Exceptional cryogenic strength-ductility synergy in Al0.3CoCrNi medium-entropy alloy through heterogeneous grain structure and nano-scale precipitates.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Asghari-Rad, P.; Park, J.; Moon, J.; Bae, J.; Zargaran, A.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 766. 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Exceptional cryogenic strength-ductility synergy in Al<inf>0.3</inf>CoCrNi medium-entropy alloy through heterogeneous grain structure and nano-scale precipitates},\n type = {article},\n year = {2019},\n keywords = {Cryogenic tensile properties,Deformation twins,Heterogeneous microstructure,High-entropy alloy,Precipitation strengthening},\n volume = {766},\n id = {5f52d329-99c9-31de-970f-c0724554b629},\n created = {2022-09-07T04:57:19.899Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:19.899Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {We engineered an Al0.3CoCrNi medium-entropy alloy with heterogeneous grain structure and nanoscale precipitation through thermo-mechanical processing route, with an aim to achieve a remarkable combination of cryogenic yield strength and ductility. The alloy exhibited an exceptional combination of high cryogenic yield strength of ∼1.1 GPa and high uniform elongation of ∼37%.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Asghari-Rad, P. and Park, J.M. and Moon, J. and Bae, J.W. and Zargaran, A. and Kim, H.S.},\n doi = {10.1016/j.msea.2019.138372},\n journal = {Materials Science and Engineering A}\n}
\n
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\n We engineered an Al0.3CoCrNi medium-entropy alloy with heterogeneous grain structure and nanoscale precipitation through thermo-mechanical processing route, with an aim to achieve a remarkable combination of cryogenic yield strength and ductility. The alloy exhibited an exceptional combination of high cryogenic yield strength of ∼1.1 GPa and high uniform elongation of ∼37%.\n
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\n \n\n \n \n \n \n \n Fine tuning of tensile properties in CrCoNi medium entropy alloy through cold rolling and annealing.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Asghari-Rad, P.; Bae, J.; and Kim, H.\n\n\n \n\n\n\n Intermetallics, 113. 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Fine tuning of tensile properties in CrCoNi medium entropy alloy through cold rolling and annealing},\n type = {article},\n year = {2019},\n keywords = {Deformation twins,Medium entropy alloy,Partial recrystallization,Tensile properties,Thermo-mechanical processing},\n volume = {113},\n id = {8bf832d3-1951-344b-86d3-78a43ac0de63},\n created = {2022-09-07T04:57:20.044Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.044Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the present study, tensile properties of CrCoNi medium entropy alloy with different microstructures (recovery, partial recrystallization, recrystallization) were investigated by subjecting cold-rolled samples to different annealing conditions. The microstructure of the cold-rolled sample showed the presence of severely deformed grains with several deformation twins. Annealing of the cold-rolled samples at 700 °C and above for 60 min led to fully recrystallized microstructure, while annealing at temperatures lower than 700 °C led to recovery and partially recrystallized microstructures. The annealed samples showed a typical strength-ductility trade-off with an increasing fraction of recrystallized grains and increasing average grain size in samples with partially recrystallized and fully recrystallized microstructure, respectively. Fine tuning of microstructure led to a remarkable combination of strength (~1 GPa) and uniform elongation (28%) in the sample with partially recrystallized microstructure, which consists of ~77% of recrystallized grains with an average recrystallized grain size of ~3 μm.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Asghari-Rad, P. and Bae, J.W. and Kim, H.S.},\n doi = {10.1016/j.intermet.2019.106578},\n journal = {Intermetallics}\n}
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\n In the present study, tensile properties of CrCoNi medium entropy alloy with different microstructures (recovery, partial recrystallization, recrystallization) were investigated by subjecting cold-rolled samples to different annealing conditions. The microstructure of the cold-rolled sample showed the presence of severely deformed grains with several deformation twins. Annealing of the cold-rolled samples at 700 °C and above for 60 min led to fully recrystallized microstructure, while annealing at temperatures lower than 700 °C led to recovery and partially recrystallized microstructures. The annealed samples showed a typical strength-ductility trade-off with an increasing fraction of recrystallized grains and increasing average grain size in samples with partially recrystallized and fully recrystallized microstructure, respectively. Fine tuning of microstructure led to a remarkable combination of strength (~1 GPa) and uniform elongation (28%) in the sample with partially recrystallized microstructure, which consists of ~77% of recrystallized grains with an average recrystallized grain size of ~3 μm.\n
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\n \n\n \n \n \n \n \n Superplasticity of V10Cr15Mn5Fe35Co10Ni25 high-entropy alloy processed using high-pressure torsion.\n \n \n \n\n\n \n Thi-Cam Nguyen, N.; Moon, J.; Sathiyamoorthi, P.; Asghari-Rad, P.; Kim, G.; Lee, C.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 764. 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Superplasticity of V<inf>10</inf>Cr<inf>15</inf>Mn<inf>5</inf>Fe<inf>35</inf>Co<inf>10</inf>Ni<inf>25</inf> high-entropy alloy processed using high-pressure torsion},\n type = {article},\n year = {2019},\n keywords = {Grain boundary sliding,High-entropy alloy,High-pressure torsion,Superplasticity},\n volume = {764},\n id = {3fafa1fe-831b-3559-9cd3-d1ddeb124bbe},\n created = {2022-09-07T04:57:20.075Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.075Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In this study, the superplasticity of nanostructured V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy processed by high-pressure torsion was investigated using high-temperature tensile testing in the temperature range of 873–1073 K and strain rate range of 5.0✕10−4 to 1.0✕10−2 s−1. The alloy exhibited extreme elongation at these elevated temperatures, with the greatest elongation of 770% at 973 K without any necking or a notable cavity in the fracture area. Other impressive achievements were also recorded (700% elongation at 1073 K and 3.3✕10−3 s−1 and 600% elongation under other conditions). The equiaxed microstructure was maintained in both the deformed and undeformed regions of the tensile specimen, demonstrating that grain-boundary sliding is the dominant mechanism of superplasticity.},\n bibtype = {article},\n author = {Thi-Cam Nguyen, N. and Moon, J. and Sathiyamoorthi, P. and Asghari-Rad, P. and Kim, G.H. and Lee, C.S. and Kim, H.S.},\n doi = {10.1016/j.msea.2019.138198},\n journal = {Materials Science and Engineering A}\n}
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\n In this study, the superplasticity of nanostructured V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy processed by high-pressure torsion was investigated using high-temperature tensile testing in the temperature range of 873–1073 K and strain rate range of 5.0✕10−4 to 1.0✕10−2 s−1. The alloy exhibited extreme elongation at these elevated temperatures, with the greatest elongation of 770% at 973 K without any necking or a notable cavity in the fracture area. Other impressive achievements were also recorded (700% elongation at 1073 K and 3.3✕10−3 s−1 and 600% elongation under other conditions). The equiaxed microstructure was maintained in both the deformed and undeformed regions of the tensile specimen, demonstrating that grain-boundary sliding is the dominant mechanism of superplasticity.\n
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\n \n\n \n \n \n \n \n Fabrication and mechanical properties of TiC reinforced CoCrFeMnNi high-entropy alloy composite by water atomization and spark plasma sintering.\n \n \n \n\n\n \n Yim, D.; Sathiyamoorthi, P.; Hong, S.; and Kim, H.\n\n\n \n\n\n\n Journal of Alloys and Compounds, 781. 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Fabrication and mechanical properties of TiC reinforced CoCrFeMnNi high-entropy alloy composite by water atomization and spark plasma sintering},\n type = {article},\n year = {2019},\n keywords = {Atomization,High-entropy alloy,Nano-composites,Powder metallurgy,TiC particles},\n volume = {781},\n id = {3116ccb7-5d69-35ac-97df-1041a06d5d1b},\n created = {2022-09-07T04:57:20.140Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.140Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In this study, the TiC-reinforced CoCrFeMnNi high-entropy alloy (HEA) composite was fabricated using water atomization (WA), mechanical milling (MM), and spark plasma sintering (SPS). The microstructural evolution and mechanical properties of TiC-reinforced HEA composite are investigated using electron backscatter diffraction, transmission electron microscopy, and room temperature compression tests. The addition of 5 wt% of TiC nano-particles to CoCrFeMnNi HEA resulted in fine grain size, high yield strength, and high strain hardening. The average grain size achieved for alloys with and without TiC after sintering is 5.1 μm and 10.6 μm, respectively. The addition of TiC increases the compressive yield strength from ∼507 MPa to ∼698 MPa and compressive fracture strength from ∼1527 MPa to ∼2216 MPa, without sacrificing the ductility. The strengthening behavior of TiC-reinforced CoCrFeMnNi HEA composite is quantitatively discussed based on grain boundary strengthening, dislocation strengthening, and dispersion strengthening. The role of TiC nano-particles in the strain hardening improvement is investigated with respect to the dislocation-particle interaction and consequently increased dislocation density.},\n bibtype = {article},\n author = {Yim, D. and Sathiyamoorthi, P. and Hong, S.-J. and Kim, H.S.},\n doi = {10.1016/j.jallcom.2018.12.119},\n journal = {Journal of Alloys and Compounds}\n}
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\n In this study, the TiC-reinforced CoCrFeMnNi high-entropy alloy (HEA) composite was fabricated using water atomization (WA), mechanical milling (MM), and spark plasma sintering (SPS). The microstructural evolution and mechanical properties of TiC-reinforced HEA composite are investigated using electron backscatter diffraction, transmission electron microscopy, and room temperature compression tests. The addition of 5 wt% of TiC nano-particles to CoCrFeMnNi HEA resulted in fine grain size, high yield strength, and high strain hardening. The average grain size achieved for alloys with and without TiC after sintering is 5.1 μm and 10.6 μm, respectively. The addition of TiC increases the compressive yield strength from ∼507 MPa to ∼698 MPa and compressive fracture strength from ∼1527 MPa to ∼2216 MPa, without sacrificing the ductility. The strengthening behavior of TiC-reinforced CoCrFeMnNi HEA composite is quantitatively discussed based on grain boundary strengthening, dislocation strengthening, and dispersion strengthening. The role of TiC nano-particles in the strain hardening improvement is investigated with respect to the dislocation-particle interaction and consequently increased dislocation density.\n
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\n \n\n \n \n \n \n \n Superior cryogenic tensile properties of ultrafine-grained CoCrNi medium-entropy alloy produced by high-pressure torsion and annealing.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Moon, J.; Bae, J.; Asghari-Rad, P.; and Kim, H.\n\n\n \n\n\n\n Scripta Materialia, 163. 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Superior cryogenic tensile properties of ultrafine-grained CoCrNi medium-entropy alloy produced by high-pressure torsion and annealing},\n type = {article},\n year = {2019},\n keywords = {CoCrNi alloy,Cryogenic tensile strength,High-pressure torsion,Nanotwins,Ultrafine-grain},\n volume = {163},\n id = {8b2fd7ef-fdf8-3173-9386-9f9b864ac2e7},\n created = {2022-09-07T04:57:20.158Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.158Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Ultrafine-grained materials with nanotwins are expected to produce a remarkable combination of strength and ductility. In the present study, ultrafine-grained CoCrNi medium-entropy alloy with nanotwins is fabricated by high-pressure torsion followed by annealing; and investigated for cryogenic tensile properties. The alloy exhibits superior cryogenic tensile properties with a tensile strength of ~2 GPa and tensile strain of ~27%. The cryogenic tensile strength of ultrafine-grained sample increased by 67% as compared to the cryogenic tensile strength of coarse-grained sample due to fine grain size, annealing nanotwins, residual dislocation density, and strong temperature dependence of yield strength.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Moon, J. and Bae, J.W. and Asghari-Rad, P. and Kim, H.S.},\n doi = {10.1016/j.scriptamat.2019.01.016},\n journal = {Scripta Materialia}\n}
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\n Ultrafine-grained materials with nanotwins are expected to produce a remarkable combination of strength and ductility. In the present study, ultrafine-grained CoCrNi medium-entropy alloy with nanotwins is fabricated by high-pressure torsion followed by annealing; and investigated for cryogenic tensile properties. The alloy exhibits superior cryogenic tensile properties with a tensile strength of ~2 GPa and tensile strain of ~27%. The cryogenic tensile strength of ultrafine-grained sample increased by 67% as compared to the cryogenic tensile strength of coarse-grained sample due to fine grain size, annealing nanotwins, residual dislocation density, and strong temperature dependence of yield strength.\n
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\n \n\n \n \n \n \n \n Plastic Deformation Behavior of 40Fe–25Ni–15Cr–10Co–10V High-Entropy Alloy for Cryogenic Applications.\n \n \n \n\n\n \n Jang, M.; Kwak, H.; Lee, Y.; Jeong, Y.; Choi, J.; Jo, Y.; Choi, W.; Sung, H.; Yoon, E.; Praveen, S.; Lee, S.; Lee, B.; Abd El Aal, M.; and Kim, H.\n\n\n \n\n\n\n Metals and Materials International, 25(2). 2019.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Plastic Deformation Behavior of 40Fe–25Ni–15Cr–10Co–10V High-Entropy Alloy for Cryogenic Applications},\n type = {article},\n year = {2019},\n keywords = {Cryogenic deformation,Deformation twinning,Finite element analysis,High-entropy alloy,Plastic deformation behavior},\n volume = {25},\n id = {b77e9531-3907-3cca-985d-b8ebac8ea4d5},\n created = {2022-09-07T04:57:20.297Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.297Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A single FCC phase 40Fe–25Ni–15Cr–10Co–10V high-entropy alloy was designed, fabricated, and evaluated for potential cryogenic applications. The alloy forms a single FCC phase and exhibits higher yield strength, tensile strength, and elongation at cryogenic temperature (77 K) than at room temperature (298 K). The superior tensile properties at cryogenic temperature are discussed based on the formation of deformation twins during the tensile test at cryogenic temperature. In addition, a constitutive model reflecting the cryogenic deformation mechanism (i.e., twinning-induced plasticity) was implemented into the finite element method to analyze this behavior. Experimental results and the finite element analysis suggest that the increase in plastic deformation capacity at cryogenic temperature contributes to the formation of deformation twins.},\n bibtype = {article},\n author = {Jang, M.J. and Kwak, H. and Lee, Y.W. and Jeong, Y. and Choi, J. and Jo, Y.H. and Choi, W.-M. and Sung, H.J. and Yoon, E.Y. and Praveen, S. and Lee, S. and Lee, B.-J. and Abd El Aal, M.I. and Kim, H.S.},\n doi = {10.1007/s12540-018-0184-6},\n journal = {Metals and Materials International},\n number = {2}\n}
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\n A single FCC phase 40Fe–25Ni–15Cr–10Co–10V high-entropy alloy was designed, fabricated, and evaluated for potential cryogenic applications. The alloy forms a single FCC phase and exhibits higher yield strength, tensile strength, and elongation at cryogenic temperature (77 K) than at room temperature (298 K). The superior tensile properties at cryogenic temperature are discussed based on the formation of deformation twins during the tensile test at cryogenic temperature. In addition, a constitutive model reflecting the cryogenic deformation mechanism (i.e., twinning-induced plasticity) was implemented into the finite element method to analyze this behavior. Experimental results and the finite element analysis suggest that the increase in plastic deformation capacity at cryogenic temperature contributes to the formation of deformation twins.\n
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\n \n\n \n \n \n \n \n Effect of grain size on the tensile behavior of V10Cr15Mn5Fe35Co10Ni25 high entropy alloy.\n \n \n \n\n\n \n Asghari-Rad, P.; Sathiyamoorthi, P.; Bae, J.; Moon, J.; Park, J.; Zargaran, A.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 744. 2019.\n \n\n\n\n
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@article{\n title = {Effect of grain size on the tensile behavior of V<inf>10</inf>Cr<inf>15</inf>Mn<inf>5</inf>Fe<inf>35</inf>Co<inf>10</inf>Ni<inf>25</inf> high entropy alloy},\n type = {article},\n year = {2019},\n keywords = {Deformation mechanism,Grain size,High-entropy alloy (HEA),Mechanical twinning,Work-hardening},\n volume = {744},\n id = {7ec40fe3-5bd7-3eb0-8ab1-a0d6353a43fd},\n created = {2022-09-07T04:57:20.297Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.297Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the present study, V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy (HEA) of a single phase face-centered cubic structure with various grain sizes was fabricated. The influences of grain size on the work-hardening behavior and deformation mechanisms were investigated. The fine-grained and coarse-grained samples showed different work hardening behaviors during room temperature tensile deformation. Microstructural analysis revealed the presence of a high-density tangled dislocation structure without any mechanical twinning in the fine-grained sample, while mechanical twinning was observed to be the additional deformation mechanism in the coarse-grained sample.},\n bibtype = {article},\n author = {Asghari-Rad, P. and Sathiyamoorthi, P. and Bae, J.W. and Moon, J. and Park, J.M. and Zargaran, A. and Kim, H.S.},\n doi = {10.1016/j.msea.2018.12.077},\n journal = {Materials Science and Engineering A}\n}
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\n In the present study, V10Cr15Mn5Fe35Co10Ni25 (at%) high-entropy alloy (HEA) of a single phase face-centered cubic structure with various grain sizes was fabricated. The influences of grain size on the work-hardening behavior and deformation mechanisms were investigated. The fine-grained and coarse-grained samples showed different work hardening behaviors during room temperature tensile deformation. Microstructural analysis revealed the presence of a high-density tangled dislocation structure without any mechanical twinning in the fine-grained sample, while mechanical twinning was observed to be the additional deformation mechanism in the coarse-grained sample.\n
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\n \n\n \n \n \n \n \n Effect of annealing on microstructure and tensile behavior of CoCrNi medium entropy alloy processed by high-pressure torsion.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Bae, J.; Asghari-Rad, P.; Park, J.; Kim, J.; and Kim, H.\n\n\n \n\n\n\n Entropy, 20(11). 2018.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n  \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Effect of annealing on microstructure and tensile behavior of CoCrNi medium entropy alloy processed by high-pressure torsion},\n type = {article},\n year = {2018},\n keywords = {High-pressure torsion,Medium entropy alloy,Partial recrystallization,Tensile strength},\n volume = {20},\n id = {87b66e69-69df-3fa7-835c-b634bcee1487},\n created = {2022-09-07T04:57:20.455Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.455Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Annealing of severely plastic deformed materials is expected to produce a good combination of strength and ductility, which has been widely demonstrated in conventional materials. In the present study, high-pressure torsion processed CoCrNi medium entropy alloy consisting of a single face-centered cubic (FCC) phase with a grain size of ~50 nm was subjected to different annealing conditions, and its effect on microstructure and mechanical behavior was investigated. The annealing of high-pressure torsion processed CoCrNi alloy exhibits partial recrystallization and near full recrystallization based on the annealing temperature and time. The samples annealed at 700 °C for 2 min exhibit very fine grain size, a high fraction of low angle grain boundaries, and high kernel average misorientation value, indicating partially recrystallized microstructure. The samples annealed for a longer duration ( > 2 min) exhibit relatively larger grain size, a low fraction of low angle grain boundaries, and low kernel average misorientation value, indicating nearly full recrystallized microstructure. The annealed samples with different microstructures significantly influence the uniform elongation, tensile strength, and work hardening rate. The sample annealed at 700 °C for 15 min exhibits a remarkable combination of tensile strength (~1090 MPa) and strain to failure (~41%).},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Bae, J.W. and Asghari-Rad, P. and Park, J.M. and Kim, J.G. and Kim, H.S.},\n doi = {10.3390/e20110849},\n journal = {Entropy},\n number = {11}\n}
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\n Annealing of severely plastic deformed materials is expected to produce a good combination of strength and ductility, which has been widely demonstrated in conventional materials. In the present study, high-pressure torsion processed CoCrNi medium entropy alloy consisting of a single face-centered cubic (FCC) phase with a grain size of ~50 nm was subjected to different annealing conditions, and its effect on microstructure and mechanical behavior was investigated. The annealing of high-pressure torsion processed CoCrNi alloy exhibits partial recrystallization and near full recrystallization based on the annealing temperature and time. The samples annealed at 700 °C for 2 min exhibit very fine grain size, a high fraction of low angle grain boundaries, and high kernel average misorientation value, indicating partially recrystallized microstructure. The samples annealed for a longer duration ( > 2 min) exhibit relatively larger grain size, a low fraction of low angle grain boundaries, and low kernel average misorientation value, indicating nearly full recrystallized microstructure. The annealed samples with different microstructures significantly influence the uniform elongation, tensile strength, and work hardening rate. The sample annealed at 700 °C for 15 min exhibits a remarkable combination of tensile strength (~1090 MPa) and strain to failure (~41%).\n
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\n \n\n \n \n \n \n \n Ultra-high tensile strength nanocrystalline CoCrNi equi-atomic medium entropy alloy processed by high-pressure torsion.\n \n \n \n\n\n \n Praveen, S.; Bae, J.; Asghari-Rad, P.; Park, J.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 735. 2018.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Ultra-high tensile strength nanocrystalline CoCrNi equi-atomic medium entropy alloy processed by high-pressure torsion},\n type = {article},\n year = {2018},\n keywords = {High entropy alloys,High-pressure torsion,Nano-grains,Nano-twins,Ultra-high tensile strength},\n volume = {735},\n id = {3ebcd11a-ce13-3b28-97f0-e038f2c0a6cb},\n created = {2022-09-07T04:57:20.456Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.456Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {A nanocrystalline CoCrNi alloy of ~50 nm grain size with the ultra-high ultimate tensile strength of ~2.2 GPa and fracture strain of ~9% was fabricated using high-pressure torsion. The presence of high density of nano-twins, stacking faults, dislocations, and nano-grains is attributed to the superior mechanical properties.},\n bibtype = {article},\n author = {Praveen, S. and Bae, J.W. and Asghari-Rad, P. and Park, J.M. and Kim, H.S.},\n doi = {10.1016/j.msea.2018.08.079},\n journal = {Materials Science and Engineering A}\n}
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\n A nanocrystalline CoCrNi alloy of ~50 nm grain size with the ultra-high ultimate tensile strength of ~2.2 GPa and fracture strain of ~9% was fabricated using high-pressure torsion. The presence of high density of nano-twins, stacking faults, dislocations, and nano-grains is attributed to the superior mechanical properties.\n
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\n \n\n \n \n \n \n \n Annealing-induced hardening in high-pressure torsion processed CoCrNi medium entropy alloy.\n \n \n \n\n\n \n Praveen, S.; Bae, J.; Asghari-Rad, P.; Park, J.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 734. 2018.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Annealing-induced hardening in high-pressure torsion processed CoCrNi medium entropy alloy},\n type = {article},\n year = {2018},\n keywords = {CoCrNi equiatomic alloy,Dislocation density,Grain boundaries,Hardening,High-pressure torsion},\n volume = {734},\n id = {572f58c5-315e-337e-a501-4f065a4084c3},\n created = {2022-09-07T04:57:20.521Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.521Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Nanocrystalline CoCrNi equiatomic alloy processed by high-pressure torsion shows annealing induced hardening at 500 °C and 600 °C. The microstructural characterization indicates the hardening phenomenon is not because of precipitation hardening. The annealing-induced hardening is explained based on the reduced dislocation density and grain boundaries relaxation.},\n bibtype = {article},\n author = {Praveen, S. and Bae, J.W. and Asghari-Rad, P. and Park, J.M. and Kim, H.S.},\n doi = {10.1016/j.msea.2018.07.107},\n journal = {Materials Science and Engineering A}\n}
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\n Nanocrystalline CoCrNi equiatomic alloy processed by high-pressure torsion shows annealing induced hardening at 500 °C and 600 °C. The microstructural characterization indicates the hardening phenomenon is not because of precipitation hardening. The annealing-induced hardening is explained based on the reduced dislocation density and grain boundaries relaxation.\n
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\n \n\n \n \n \n \n \n Phase evolution and thermal stability of AlCoCrFe high entropy alloy with carbon as unsolicited addition from milling media.\n \n \n \n\n\n \n Praveen, S.; Anupam, A.; Tilak, R.; and Kottada, R.\n\n\n \n\n\n\n Materials Chemistry and Physics, 210. 2018.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Phase evolution and thermal stability of AlCoCrFe high entropy alloy with carbon as unsolicited addition from milling media},\n type = {article},\n year = {2018},\n keywords = {High entropy alloy,Mechanical alloying,Spark plasma sintering,Thermal stability},\n volume = {210},\n id = {20fb68cf-b0ba-3e4a-92fc-4437f829222a},\n created = {2022-09-07T04:57:20.526Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.526Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Phase evolution and thermal stability of AlCoCrFe high entropy alloy with unsolicited carbon from the milling media were investigated. A single BCC phase was evolved during mechanical alloying, and BCC/B2 phases with Cr-rich M23C6 carbide was observed after spark plasma sintering. Unsolicited carbon during milling has led to the formation of M23C6 secondary phase after sintering. The alloy exhibits a very high hardness of 1050 ± 20 HV1 and excellent phase stability. The hardness reduction after annealing at 900 °C for 600 h is less than 10%, indicating excellent resistance to anneal softening.},\n bibtype = {article},\n author = {Praveen, S. and Anupam, A. and Tilak, R. and Kottada, R.S.},\n doi = {10.1016/j.matchemphys.2017.10.040},\n journal = {Materials Chemistry and Physics}\n}
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\n Phase evolution and thermal stability of AlCoCrFe high entropy alloy with unsolicited carbon from the milling media were investigated. A single BCC phase was evolved during mechanical alloying, and BCC/B2 phases with Cr-rich M23C6 carbide was observed after spark plasma sintering. Unsolicited carbon during milling has led to the formation of M23C6 secondary phase after sintering. The alloy exhibits a very high hardness of 1050 ± 20 HV1 and excellent phase stability. The hardness reduction after annealing at 900 °C for 600 h is less than 10%, indicating excellent resistance to anneal softening.\n
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\n \n\n \n \n \n \n \n High-temperature tensile deformation behavior of hot rolled CrMnFeCoNi high-entropy alloy.\n \n \n \n\n\n \n Jang, M.; Praveen, S.; Sung, H.; Bae, J.; Moon, J.; and Kim, H.\n\n\n \n\n\n\n Journal of Alloys and Compounds, 730. 2018.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {High-temperature tensile deformation behavior of hot rolled CrMnFeCoNi high-entropy alloy},\n type = {article},\n year = {2018},\n keywords = {Dynamic recrystallization,Flow behavior,High-entropy alloy,High-temperature tensile deformation,Mechanical properties,Steady-state flow stress},\n volume = {730},\n id = {a5d0f4e5-8795-34c8-9ca8-f0e733bd237e},\n created = {2022-09-07T04:57:20.600Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.600Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the present study, high temperature (700–1100 °C) tensile deformation behavior of hot-rolled CrMnFeCoNi high-entropy alloy was investigated. A single face-centered cubic phase was retained in the hot deformed specimens under different deformation conditions. The flow behavior was significantly influenced by temperature and microstructure evolution. A strong temperature dependence of yield stress was observed with a drastic drop in yield strength from 413 MPa at 700 °C to 94 MPa at 900 °C. A profound increase in ductility was observed above 700 °C and a perceptive decrease in ductility was observed above 900 °C. Electron backscatter diffraction analysis indicates incomplete dynamic recrystallization at 700 °C leading to a significant difference in the flow behavior.},\n bibtype = {article},\n author = {Jang, M.J. and Praveen, S. and Sung, H.J. and Bae, J.W. and Moon, J. and Kim, H.S.},\n doi = {10.1016/j.jallcom.2017.09.293},\n journal = {Journal of Alloys and Compounds}\n}
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\n In the present study, high temperature (700–1100 °C) tensile deformation behavior of hot-rolled CrMnFeCoNi high-entropy alloy was investigated. A single face-centered cubic phase was retained in the hot deformed specimens under different deformation conditions. The flow behavior was significantly influenced by temperature and microstructure evolution. A strong temperature dependence of yield stress was observed with a drastic drop in yield strength from 413 MPa at 700 °C to 94 MPa at 900 °C. A profound increase in ductility was observed above 700 °C and a perceptive decrease in ductility was observed above 900 °C. Electron backscatter diffraction analysis indicates incomplete dynamic recrystallization at 700 °C leading to a significant difference in the flow behavior.\n
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\n \n\n \n \n \n \n \n High-Entropy Alloys: Potential Candidates for High-Temperature Applications – An Overview.\n \n \n \n\n\n \n Praveen, S.; and Kim, H.\n\n\n \n\n\n\n Advanced Engineering Materials, 20(1). 2018.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {High-Entropy Alloys: Potential Candidates for High-Temperature Applications – An Overview},\n type = {article},\n year = {2018},\n keywords = {High-entropy alloys,age hardening,high-temperature mechanical properties,microstructural stability,sluggish diffusion},\n volume = {20},\n id = {a33956ff-478e-3265-b0b3-aa60059ed67c},\n created = {2022-09-07T04:57:20.607Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.607Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Multi-principal elemental alloys, commonly referred to as high-entropy alloys (HEAs), are a new class of emerging advanced materials with novel alloy design concept. Unlike the design of conventional alloys, which is based on one or at most two principal elements, the design of HEA is based on multi-principal elements in equal or near-equal atomic ratio. The advent of HEA has revived the alloy design perception and paved the way to produce an ample number of compositions with different combinations of promising properties for a variety of structural applications. Among the properties possessed by HEAs, sluggish diffusion and strength retention at elevated temperature have caught wide attention. The need to develop new materials for high-temperature applications with superior high-temperature properties over superalloys has been one of the prime concerns of the high-temperature materials research community. The current article shows that HEAs have the potential to replace Ni-base superalloys as the next generation high-temperature materials. This review focuses on the phase stability, microstructural stability, and high-temperature mechanical properties of HEAs. This article will be highly beneficial for materials engineering and science community whose interest is in the development and understanding of HEAs for high-temperature applications.},\n bibtype = {article},\n author = {Praveen, S. and Kim, H.S.},\n doi = {10.1002/adem.201700645},\n journal = {Advanced Engineering Materials},\n number = {1}\n}
\n
\n\n\n
\n Multi-principal elemental alloys, commonly referred to as high-entropy alloys (HEAs), are a new class of emerging advanced materials with novel alloy design concept. Unlike the design of conventional alloys, which is based on one or at most two principal elements, the design of HEA is based on multi-principal elements in equal or near-equal atomic ratio. The advent of HEA has revived the alloy design perception and paved the way to produce an ample number of compositions with different combinations of promising properties for a variety of structural applications. Among the properties possessed by HEAs, sluggish diffusion and strength retention at elevated temperature have caught wide attention. The need to develop new materials for high-temperature applications with superior high-temperature properties over superalloys has been one of the prime concerns of the high-temperature materials research community. The current article shows that HEAs have the potential to replace Ni-base superalloys as the next generation high-temperature materials. This review focuses on the phase stability, microstructural stability, and high-temperature mechanical properties of HEAs. This article will be highly beneficial for materials engineering and science community whose interest is in the development and understanding of HEAs for high-temperature applications.\n
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\n  \n 2017\n \n \n (2)\n \n \n
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\n \n\n \n \n \n \n \n Shock wave compaction and sintering of mechanically alloyed CoCrFeMnNi high-entropy alloy powders.\n \n \n \n\n\n \n Yim, D.; Kim, W.; Praveen, S.; Jang, M.; Bae, J.; Moon, J.; Kim, E.; Hong, S.; and Kim, H.\n\n\n \n\n\n\n Materials Science and Engineering A, 708. 2017.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Shock wave compaction and sintering of mechanically alloyed CoCrFeMnNi high-entropy alloy powders},\n type = {article},\n year = {2017},\n keywords = {Compaction,High-entropy alloy,Powder metallurgy,Shock wave compaction,Sintering},\n volume = {708},\n id = {33722fd0-9165-3bf6-86c1-ee8c71de44b4},\n created = {2022-09-07T04:57:20.669Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.669Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In this study, mechanically alloyed CoCrFeMnNi high-entropy alloy (HEA) powders were compacted using static and shock wave compaction methods followed by pressureless sintering. The microstructural evolution and the mechanical properties were analyzed using optical microscopy, scanning electron microscopy, finite element method simulations, and tensile tests. The alloy consists of an FCC phase with a minor amount of ZrO2 in the as-milled and sintered condition. The presence of ZrO2 is due to the contamination during milling, and it led to the formation of composite microstructure after sintering. The static compaction of the alloyed powders resulted in an increase in compaction density (~ 85 to 88%) with the increasing pressure (1–3 GPa), and the shock wave compaction of the alloyed powders resulted in the high relative density (~ 95%) with relatively fine and isolated pores. After sintering, almost full densification (~ 99.5%) with smaller grain size and better mechanical properties was achieved in the shock wave compacted specimens as compared to the sintering of static compacted specimens. The sintered shock wave compacted specimen exhibited high yield strength of ~ 630 MPa and uniform strain distributions.},\n bibtype = {article},\n author = {Yim, D. and Kim, W. and Praveen, S. and Jang, M.J. and Bae, J.W. and Moon, J. and Kim, E. and Hong, S.-J. and Kim, H.S.},\n doi = {10.1016/j.msea.2017.09.132},\n journal = {Materials Science and Engineering A}\n}
\n
\n\n\n
\n In this study, mechanically alloyed CoCrFeMnNi high-entropy alloy (HEA) powders were compacted using static and shock wave compaction methods followed by pressureless sintering. The microstructural evolution and the mechanical properties were analyzed using optical microscopy, scanning electron microscopy, finite element method simulations, and tensile tests. The alloy consists of an FCC phase with a minor amount of ZrO2 in the as-milled and sintered condition. The presence of ZrO2 is due to the contamination during milling, and it led to the formation of composite microstructure after sintering. The static compaction of the alloyed powders resulted in an increase in compaction density (~ 85 to 88%) with the increasing pressure (1–3 GPa), and the shock wave compaction of the alloyed powders resulted in the high relative density (~ 95%) with relatively fine and isolated pores. After sintering, almost full densification (~ 99.5%) with smaller grain size and better mechanical properties was achieved in the shock wave compacted specimens as compared to the sintering of static compacted specimens. The sintered shock wave compacted specimen exhibited high yield strength of ~ 630 MPa and uniform strain distributions.\n
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\n \n\n \n \n \n \n \n Thermal stability and grain boundary strengthening in ultrafine-grained CoCrFeNi high entropy alloy composite.\n \n \n \n\n\n \n Sathiyamoorthi, P.; Basu, J.; Kashyap, S.; Pradeep, K.; and Kottada, R.\n\n\n \n\n\n\n Materials and Design, 134. 2017.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Thermal stability and grain boundary strengthening in ultrafine-grained CoCrFeNi high entropy alloy composite},\n type = {article},\n year = {2017},\n keywords = {Atom probe tomography,Grain growth, strengthening,High entropy alloy,Thermal stability},\n volume = {134},\n id = {b840739c-e353-33a4-94f2-e6127723cd65},\n created = {2022-09-07T04:57:20.675Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.675Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Thermal stability of CoCrFeNi high entropy alloy in as-milled and sintered conditions was investigated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, and atom probe tomography. Composite microstructure consists of FCC and carbide with a fine dispersion of oxide was observed in the sintered condition. Unsolicited contamination of carbon and oxygen in the as-milled powder due to the milling medium had led to the formation of composite microstructure. An exceptional thermal stability was observed upon exposure of sintered compact to higher temperatures (0.56 Tm to 0.68 Tm) for the prolonged duration of 600 h. Sintered compact exposed to 700 °C (0.56 Tm) for 600 h showed negligible change in hardness and grain size. Analysis based on the modified Hall-Petch model for two phase alloy indicates the phase boundaries act as a strong obstacle while the major contribution to strengthening comes from grain boundaries.},\n bibtype = {article},\n author = {Sathiyamoorthi, P. and Basu, J. and Kashyap, S. and Pradeep, K.G. and Kottada, R.S.},\n doi = {10.1016/j.matdes.2017.08.053},\n journal = {Materials and Design}\n}
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\n\n\n
\n Thermal stability of CoCrFeNi high entropy alloy in as-milled and sintered conditions was investigated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, and atom probe tomography. Composite microstructure consists of FCC and carbide with a fine dispersion of oxide was observed in the sintered condition. Unsolicited contamination of carbon and oxygen in the as-milled powder due to the milling medium had led to the formation of composite microstructure. An exceptional thermal stability was observed upon exposure of sintered compact to higher temperatures (0.56 Tm to 0.68 Tm) for the prolonged duration of 600 h. Sintered compact exposed to 700 °C (0.56 Tm) for 600 h showed negligible change in hardness and grain size. Analysis based on the modified Hall-Petch model for two phase alloy indicates the phase boundaries act as a strong obstacle while the major contribution to strengthening comes from grain boundaries.\n
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\n  \n 2016\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n Exceptional resistance to grain growth in nanocrystalline CoCrFeNi high entropy alloy at high homologous temperatures.\n \n \n \n\n\n \n Praveen, S.; Basu, J.; Kashyap, S.; and Kottada, R.\n\n\n \n\n\n\n Journal of Alloys and Compounds, 662. 2016.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Exceptional resistance to grain growth in nanocrystalline CoCrFeNi high entropy alloy at high homologous temperatures},\n type = {article},\n year = {2016},\n keywords = {Grain growth,High entropy alloy,Mechanical alloying,Spark plasma sintering,Transmission electron microscopy (TEM)},\n volume = {662},\n id = {a9de18cb-fe94-322a-8f0e-25dcdcaeb944},\n created = {2022-09-07T04:57:20.735Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.735Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Nanocrystalline CoCrFeNi high entropy alloy, synthesized by mechanical alloying followed by spark plasma sintering, demonstrated extremely sluggish grain growth even at very high homologous temperature of 0.68 Tm (900 °C) for annealing duration of 600 h. Mechanically alloyed powder had carbon and oxygen as impurities, which in turn led to the formation of two-phase mixture of FCC and Cr-rich carbide with fine distribution of Cr-rich oxide during spark plasma sintering. Sluggish grain growth is attributed to the Zener pinning effect from the fine dispersion of oxide, mutual retardation of grain boundaries in the presence of two phases, and sluggish diffusivity because of cooperative diffusion of multi-principle elements.},\n bibtype = {article},\n author = {Praveen, S. and Basu, J. and Kashyap, S. and Kottada, R.S.},\n doi = {10.1016/j.jallcom.2015.12.020},\n journal = {Journal of Alloys and Compounds}\n}
\n
\n\n\n
\n Nanocrystalline CoCrFeNi high entropy alloy, synthesized by mechanical alloying followed by spark plasma sintering, demonstrated extremely sluggish grain growth even at very high homologous temperature of 0.68 Tm (900 °C) for annealing duration of 600 h. Mechanically alloyed powder had carbon and oxygen as impurities, which in turn led to the formation of two-phase mixture of FCC and Cr-rich carbide with fine distribution of Cr-rich oxide during spark plasma sintering. Sluggish grain growth is attributed to the Zener pinning effect from the fine dispersion of oxide, mutual retardation of grain boundaries in the presence of two phases, and sluggish diffusivity because of cooperative diffusion of multi-principle elements.\n
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\n  \n 2015\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi.\n \n \n \n\n\n \n Ang, A.; Berndt, C.; Sesso, M.; Anupam, A.; S, P.; Kottada, R.; and Murty, B.\n\n\n \n\n\n\n Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 46(2). 2015.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n
@article{\n title = {Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi},\n type = {article},\n year = {2015},\n volume = {46},\n id = {d70bb01e-eb99-3c45-8d9c-d7ab6225aabb},\n created = {2022-09-07T04:57:20.741Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.741Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.},\n bibtype = {article},\n author = {Ang, A.S.M. and Berndt, C.C. and Sesso, M.L. and Anupam, A. and S, P. and Kottada, R.S. and Murty, B.S.},\n doi = {10.1007/s11661-014-2644-z},\n journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science},\n number = {2}\n}
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\n High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.\n
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\n  \n 2014\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n Effect of molybdenum and niobium on the phase formation and hardness of nanocrystalline CoCrFeNi high entropy alloys.\n \n \n \n\n\n \n Praveen, S.; Murty, B.; and Kottada, R.\n\n\n \n\n\n\n Journal of Nanoscience and Nanotechnology, 14(10). 2014.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n \n \n\n\n\n
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@article{\n title = {Effect of molybdenum and niobium on the phase formation and hardness of nanocrystalline CoCrFeNi high entropy alloys},\n type = {article},\n year = {2014},\n keywords = {Hardness retention,Mechanical alloying,Phase formation,Spark plasma sintering},\n volume = {14},\n id = {bec25305-02ca-314c-a814-88e8528f37c7},\n created = {2022-09-07T04:57:20.794Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.794Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the present study, influence of molybdenum and niobium additions on phase formation during mechanical alloying and spark plasma sintering of CoCrFeNi high entropy alloy was studied. Major FCC and minor BCC phase were observed after mechanical alloying of CoCrFeNi. However, major FCC and sigma phase were observed after spark plasma sintering. A maximum relative density of 95% was obtained with the hardness of 570 HV in CoCrFeNi HEA. The phase formation behavior was not significantly affected by the addition of molybdenum or niobium. However, addition of Mo to CoCrFeNi increased the hardness from 570 HV to 620 HV, and the hardness increased to 710 HV with combined addition of molybdenum and niobium. After sintering, major FCC phase with crystallite size of 60-70 nm was observed in all the compositions. Further, the microstructure and hardness retention was observed in CoCrFeNiMo0.2 with annealing temperature up to 800°C.},\n bibtype = {article},\n author = {Praveen, S. and Murty, B.S. and Kottada, R.S.},\n doi = {10.1166/jnn.2014.9441},\n journal = {Journal of Nanoscience and Nanotechnology},\n number = {10}\n}
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\n In the present study, influence of molybdenum and niobium additions on phase formation during mechanical alloying and spark plasma sintering of CoCrFeNi high entropy alloy was studied. Major FCC and minor BCC phase were observed after mechanical alloying of CoCrFeNi. However, major FCC and sigma phase were observed after spark plasma sintering. A maximum relative density of 95% was obtained with the hardness of 570 HV in CoCrFeNi HEA. The phase formation behavior was not significantly affected by the addition of molybdenum or niobium. However, addition of Mo to CoCrFeNi increased the hardness from 570 HV to 620 HV, and the hardness increased to 710 HV with combined addition of molybdenum and niobium. After sintering, major FCC phase with crystallite size of 60-70 nm was observed in all the compositions. Further, the microstructure and hardness retention was observed in CoCrFeNiMo0.2 with annealing temperature up to 800°C.\n
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\n  \n 2013\n \n \n (2)\n \n \n
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\n \n\n \n \n \n \n \n Phase evolution and densification behavior of nanocrystalline multicomponent high entropy alloys during spark plasma sintering.\n \n \n \n\n\n \n Praveen, S.; Murty, B.; and Kottada, R.\n\n\n \n\n\n\n JOM, 65(12). 2013.\n \n\n\n\n
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@article{\n title = {Phase evolution and densification behavior of nanocrystalline multicomponent high entropy alloys during spark plasma sintering},\n type = {article},\n year = {2013},\n volume = {65},\n id = {6a85860d-2d00-3417-8a56-08fed9f587a4},\n created = {2022-09-07T04:57:20.804Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.804Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {In the current study, the phase evolution of multicomponent equiatomic CoCrCuFeNi, CoCuFeNi, CoCrCuNi, and CoCrFeNi alloys synthesized by mechanical alloying (MA) followed by annealing was studied. From the phase evolution studies, CoCrFeNi, CoFeMnNi, CoCuFeNi, and CoFeNi were chosen to correlate the densification together with phase evolution during spark plasma sintering (SPS). MA resulted in a major face centered cubic (fcc) phase and a minor body centered cubic (bcc) phase in Cr-containing alloys, and a single fcc phase in all other alloys. After SPS, CoFeMnNi and CoFeNi remained as single fcc phase. However, CoCuFeNi transformed to two fcc phases, and CoCrFeNi had a major fcc phase with minor sigma phase. From densification studies, it was evident that CoCrFeNi showed delayed densification, albeit maximum final densification in comparison to other alloys. This behavior was attributed to distinctly different phase evolution in CoCrFeNi during SPS as compared to other alloys. Detailed phase evolution studies were carried out on CoCrFeNi by annealing the powders at different temperatures followed by conventional x-ray diffraction (XRD) and in situ high-temperature XRD of mechanically alloyed powders. The results obtained from the annealing and in situ high-temperature XRD studies were correlated with the densification and alloying behavior of CoCrFeNi alloy. © 2013 The Minerals, Metals & Materials Society.},\n bibtype = {article},\n author = {Praveen, S. and Murty, B.S. and Kottada, R.S.},\n doi = {10.1007/s11837-013-0759-0},\n journal = {JOM},\n number = {12}\n}
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\n In the current study, the phase evolution of multicomponent equiatomic CoCrCuFeNi, CoCuFeNi, CoCrCuNi, and CoCrFeNi alloys synthesized by mechanical alloying (MA) followed by annealing was studied. From the phase evolution studies, CoCrFeNi, CoFeMnNi, CoCuFeNi, and CoFeNi were chosen to correlate the densification together with phase evolution during spark plasma sintering (SPS). MA resulted in a major face centered cubic (fcc) phase and a minor body centered cubic (bcc) phase in Cr-containing alloys, and a single fcc phase in all other alloys. After SPS, CoFeMnNi and CoFeNi remained as single fcc phase. However, CoCuFeNi transformed to two fcc phases, and CoCrFeNi had a major fcc phase with minor sigma phase. From densification studies, it was evident that CoCrFeNi showed delayed densification, albeit maximum final densification in comparison to other alloys. This behavior was attributed to distinctly different phase evolution in CoCrFeNi during SPS as compared to other alloys. Detailed phase evolution studies were carried out on CoCrFeNi by annealing the powders at different temperatures followed by conventional x-ray diffraction (XRD) and in situ high-temperature XRD of mechanically alloyed powders. The results obtained from the annealing and in situ high-temperature XRD studies were correlated with the densification and alloying behavior of CoCrFeNi alloy. © 2013 The Minerals, Metals & Materials Society.\n
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\n \n\n \n \n \n \n \n Characterization of oxide dispersed AlCoCrFe high entropy alloy synthesized by mechanical alloying and spark plasma sintering.\n \n \n \n\n\n \n Praveen, S.; Anupam, A.; Sirasani, T.; Murty, B.; and Kottada, R.\n\n\n \n\n\n\n Transactions of the Indian Institute of Metals, 66(4). 2013.\n \n\n\n\n
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@article{\n title = {Characterization of oxide dispersed AlCoCrFe high entropy alloy synthesized by mechanical alloying and spark plasma sintering},\n type = {article},\n year = {2013},\n keywords = {Mechanical alloying,Oxide dispersion,Phase evolution,Solid solution strengthening effect},\n volume = {66},\n id = {1855db21-e927-3468-885e-eb2dc154d6b7},\n created = {2022-09-07T04:57:20.853Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.853Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {The present study deals with phase evolution of oxide dispersed AlCoCrFe high entropy alloy during mechanical alloying and spark plasma sintering. Mechanical alloying of AlCoCrFe resulted in a single BCC phase. However, ordering of BCC phase with evolution of chromium carbide and sigma phase were observed after spark plasma sintering. High hardness of 1,050 ± 20 HV1 and 1,070 ± 20 HV1 was observed for AlCoCrFe high entropy alloy without and with oxide dispersion, respectively. Significant contribution from solid solution strengthening effect in high entropy alloys appears to have overwhelmed the effect of oxide dispersion on hardness. © 2013 Indian Institute of Metals.},\n bibtype = {article},\n author = {Praveen, S. and Anupam, A. and Sirasani, T. and Murty, B.S. and Kottada, R.S.},\n doi = {10.1007/s12666-013-0268-4},\n journal = {Transactions of the Indian Institute of Metals},\n number = {4}\n}
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\n The present study deals with phase evolution of oxide dispersed AlCoCrFe high entropy alloy during mechanical alloying and spark plasma sintering. Mechanical alloying of AlCoCrFe resulted in a single BCC phase. However, ordering of BCC phase with evolution of chromium carbide and sigma phase were observed after spark plasma sintering. High hardness of 1,050 ± 20 HV1 and 1,070 ± 20 HV1 was observed for AlCoCrFe high entropy alloy without and with oxide dispersion, respectively. Significant contribution from solid solution strengthening effect in high entropy alloys appears to have overwhelmed the effect of oxide dispersion on hardness. © 2013 Indian Institute of Metals.\n
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\n \n\n \n \n \n \n \n Alloying behavior in multi-component AlCoCrCuFe and NiCoCrCuFe high entropy alloys.\n \n \n \n\n\n \n Praveen, S.; Murty, B.; and Kottada, R.\n\n\n \n\n\n\n Materials Science and Engineering A, 534. 2012.\n \n\n\n\n
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@article{\n title = {Alloying behavior in multi-component AlCoCrCuFe and NiCoCrCuFe high entropy alloys},\n type = {article},\n year = {2012},\n keywords = {Hardness measurement,High entropy alloys,Mechanical alloying,Nanostructured materials,Ordering,X-ray diffraction},\n volume = {534},\n id = {fea77a5b-cd77-3c27-b84a-a74c6124e372},\n created = {2022-09-07T04:57:20.856Z},\n file_attached = {false},\n profile_id = {19feee0a-83ed-3c3a-96fa-9146fe4d6ab1},\n last_modified = {2022-09-07T04:57:20.856Z},\n read = {false},\n starred = {false},\n authored = {true},\n confirmed = {false},\n hidden = {false},\n private_publication = {true},\n abstract = {Multi-component high entropy alloys (HEAs) are observed to form simple solid solutions in contrary to general perception that complex compounds may form in such multi-component equi-atomic alloys. In the present study, alloying behavior was investigated using XRD in AlCoCrCuFe and NiCoCrCuFe equi-atomic high entropy alloys synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). Simple FCC and BCC phases evolved after MA, while Cu-rich FCC and sigma (σ) phases evolved along with FCC and BCC phases after SPS. Further, NiCoCuFe, NiCoCrFe and NiCoFe equi-atomic alloys were investigated to confirm the formation of Cu-rich FCC, and σ phases. The hardness was observed to be 770 ± 10. HV for AlCoCrCuFe and 400 ± 10. HV for NiCoCrCuFe. Phase evolution after MA and SPS indicate that configurational entropy is not sufficient enough to suppress the formation of Cu-rich FCC, and σ phases, and enthalpy of mixing appears to play an important role in determining the phase formation in high entropy alloys after sintering. © 2011 Elsevier B.V.},\n bibtype = {article},\n author = {Praveen, S. and Murty, B.S. and Kottada, R.S.},\n doi = {10.1016/j.msea.2011.11.044},\n journal = {Materials Science and Engineering A}\n}
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\n Multi-component high entropy alloys (HEAs) are observed to form simple solid solutions in contrary to general perception that complex compounds may form in such multi-component equi-atomic alloys. In the present study, alloying behavior was investigated using XRD in AlCoCrCuFe and NiCoCrCuFe equi-atomic high entropy alloys synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). Simple FCC and BCC phases evolved after MA, while Cu-rich FCC and sigma (σ) phases evolved along with FCC and BCC phases after SPS. Further, NiCoCuFe, NiCoCrFe and NiCoFe equi-atomic alloys were investigated to confirm the formation of Cu-rich FCC, and σ phases. The hardness was observed to be 770 ± 10. HV for AlCoCrCuFe and 400 ± 10. HV for NiCoCrCuFe. Phase evolution after MA and SPS indicate that configurational entropy is not sufficient enough to suppress the formation of Cu-rich FCC, and σ phases, and enthalpy of mixing appears to play an important role in determining the phase formation in high entropy alloys after sintering. © 2011 Elsevier B.V.\n
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