Superplasticity of a Ti-48Al-2.3Cr-0.2Mo Alloy

摘要

Superplastic behaviors of a Ti-48Al-2.3Cr-0.2Mo alloy with the initial grain size of 0.6um, resulting from 3-steps forging, have been investigated at temperatures ranging from 950°C to 1100°C and at strain rates ranging from 8×10~(-5) s~(-1) to 2×l0~(-4) s~(-1). The elongations above 500% were obtained at 1050°C-1100°C. An maximum elongation of 566% was obtained at 1050°Cand at a strain rate of 8×10~(-5) s~(-1). The flow softening and continuous strain hardening were observed in the curves of true stress-true strain, it is suggested dynamic recrystallization and high-density dislocation caused by pre-deformation are the reasons. By OA, TEM, microstructure evolutions during the deformation were observed. It is found that after superplastic deformation, the grain size become smaller, and the distribution of grain size become more uniform, the densities of dislocations become lower and the dislocations mainly distributed in the areas near grain triple junction. Grain boundary sliding accommodated by dislocation slip is the predominant deformation mechanism.