Numerical and experimental study on peritectic transition in TiAl-Nb alloys

Abstract

Abstract The solidification pathway and peritectic transition characteristic related to the solute concentration in TiAl-Nb system are calculated using the Thermo-Calc software. The results show that there are four typical solidification modes in the TiAl-Nb system, which are single β, hypo-peritectic, hyper-peritectic and single α solidification. The mole fraction of peritectic growth αp can be used to describe the undergoing extent of the peritectic tranformation (EPT) directly for the alloys with the peritectic transition, and βp/βmax can also be used to describe the EPT for the hypo-peritectic and Lp/(1\u202f−\u202fβmax) for the hyper-peritectic. The mole fraction of αp shows a parabolic shape variation on a plot of solute Al at constant Nb content. The composition of the complete peritectic transformation (PT) is around 46.5 at.% Al for the TiAl binary alloy, and it gradually shifts to the direction of high Nb content with increase of solute Al. A temperature gap (△Tp) corresponding to the peritectic transition exists in Nb containing TiAl alloys and the △Tp shows a parabolic shape on a plot of solute Al at constant Nb content. The experimental results are generally in accordance with the theoretical rules.