Influence of Microstructure Change on the Superplastic Properties of Ti₃Al Base Alloy

The superplastic properties of Ti3Al base alloy have been investigated in the range of 900~1020°C and strain rate range of 3.3×10-4~3.3×10-2s-1 .The largest elongation of 1570% was obtained under the optimal superplastic deformation condition of 980°C and 3.3×10-4 s-1. The m-value varied from 0.46 to 0.59, its maximum value was obtained at 980°C.The microstructure of the alloy after heat treatment was composed of two phases of small spherical α2 phase particles distributing in βtransus matrix. Microstructure change has an obvious effect on the superplastic properties of Ti3Al-based alloy. At 980°C,when theα2 phase grain size changed from large to small then large and the cavitations in the fracture surface were larger and deeper with decreasing strain rate, the alloy showed the larger elongation and the lower flow stress.