Abstract:The effects of initial microstructure on the flow stress, strain rate sensitivity (m), strain hardening exponent (n), apparent activation energy (Q) for deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy were investigated using isothermal compression tests. Results show that the alloy with Widmanst？tten alpha plates shows a higher peak stress and flow softening. Additionally, the alloy with equiaxed primary alpha exhibits an early yield drop at or above 810 °C and at strain rates of 0.1-5.0 s^-1. In the strain range of 0.5-0.7, m of the alloy with equiaxed primary alpha is found to be larger at 0.01 s^-1 and lower deformation temperatures. This phenomenon could be reasonably explained based on the microstructure evolution. The strain has a significant effect on n of the alloy with Widmanst？tten alpha plates, which is attributed to platelet bending/kinking and dynamic globularization of α phase. In the strain range of 0.15-0.55, Q of the alloy with Widmanst？tten alpha plates is larger.

Key words: titanium alloy; isothermal compression; flow stress; microstructure evolution; dynamic globularization