Effect of strain rate on superplasticity of TA15 titanium alloy

Influences of strain rate on superplasticity of TA15 alloy were investigated by constant strainrate tensile method. The results show that the elongation is increased gradually with decreasing in strain rate at 900°C and strain rate in range of 3.3 × 10 ^-4~1.1 × 10 ^-2 s ^-1, and the maximum elongation of 1074% can be observed, and the better superplasticity can be also obtained at the high strain rate. Moreover, the extensive strain hardening stages appear in the curves of strain-stress. The lower the strain rate is, the longer the strain hardening stage is, and it is in favor of superplastic deformation. The microstructure observation shows that the strain rate is closely related with microstructure evolution. The lower the strain rate is, the more serious the microstructure coarsening is. Additionally, at the high stain rate, lots of new fine equaxied α phase appear in the deformed region of the specimen as a result of dynamic recrystallization.