Pathways for microstructural development in TiAl. Graves, J., A., Bendersky, L., A., Biancaniello, F., S., Perepezko, J., H., & Boettinger, W., J. Materials Science and Engineering, 98(C):265-268, 1988.
Pathways for microstructural development in TiAl [pdf]Paper  abstract   bibtex   
Rapid solidification processing (RSP) of intermetallic alloys can provide alternative solidification paths and lead to the formation of metastable products. For the intermetallic TiAl with an equilibrium L10 structure, RSP has yielded a metastable hexagonal close packed (h.c.p.) α-Ti phase in both fine powder and melt-spun ribbon. Based on transmission electron microscopy observations of a fine antiphase domain structure, the h.c.p. phase orders to the Ti3Al (DO19) structure following solidification. A metastable phase diagram analysis indicates that a melt undercooling of about 100 °C is required for partitionless formation of an h.c.p. phase from an equiatomic melt and reveals other possible solidification pathways including the nucleation of metastable disordered body-centered cubic (b.c.c.) and face-centered cubic (f.c.c.) phases. Each of the potential pathways offers further opportunity for microstructural modification by solid-state annealing treatments. © 1988.

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