Solidification behavior of γ-aluminide Ti-46.5Al-xNb-yCr-zMo-0.3B alloys

Present work describes the solidification behavior of six gamma-TiAl alloys of Ti-Al-Nb-Cr-Mo-B system containing 46.5 at.% Al with varying beta stabilizing elements such as Nb, Cr and Mo in as-cast condition. All the alloys solidify through L + beta phase field with beta as the primary, alpha and gamma as secondary solidification products. The subsequent solid state transformation reactions beta -> beta + gamma, alpha + beta -> gamma and alpha -> alpha + gamma occur giving rise to various microstructural constituents such as precipitation of gamma within beta phase, peritectoid rim of gamma around beta and lamellar structure, respectively. The alloys were melted multiple times in non consumable vacuum arc melting furnace to increase homogeneity of the alloys. The addition of controlled amount of beta stabilizing elements have altered the solidification path of the present alloys from L + beta -> alpha to L + beta -> alpha + beta phase field with fine microstructure which may be used as guide line for further alloy development.