Microstructure evolution in directionally solidified Ti-(50, 52) at%Al alloys

Ti-(50, 52) at%Al alloys were directionally solidified over a wide range of growth velocities. Detailed microstructure evolution was investigated. For Ti-50Al alloys, growths of primary α phase dominated. Only a little peritectic γ phase was found in intercellular or interdendritic regions. For Ti-52Al alloys, corporative growths of both phases were observed. Primary α transformed from cells to dendrites with increase of growth velocities, and γ showed a faceted-growth pattern. The peritectic reaction became dominated when α grew as dendrites at a relatively high velocity. The lamellar orientation evolution was also investigated, which was history-dependant on that in non-melted as-cast crystals.