Flow Stress Characteristics and Microstructure Evolution During Hot Compression of Ti-62A Alloy

The hot deformation behavior and dynamic recrystallization (DRX) of Ti-62A alloy at 800, 850, 900 and 950℃ and strain rates of 0.001, 0.01, 0.1 and 1 s-1 were studied by hot compression experiments on Gleeble-3800 thermal simulator. The results show that the flow stress of Ti-62A alloy is significantly affected by strain rate and deformation temperature. The flow stress decreases with the increase of temperature and the decrease of strain rate. At 900~950℃ and strain rate of 0.01~1 s-1, the thermal deformation stress-strain curve of Ti-62A alloy belongs to dynamic recovery type, and the thermal deformation mechanism of the alloy is mainly controlled by dislocation movement, and its dynamic softening mechanism includes grain boundary sliding, dislocation cancellation and climbing mechanism. During hot deformation of Ti-62A alloy, dynamic recrystallization are more likely to occur at higher temperatures and lower strain rates, i.e. 950℃ and 0.001 s-1. Based on the classical dislocation density theory and DRX dynamics theory, a two-stage constitutive model of work hardening-dynamic recovery and DRX softening effect is established. The simulation results of DEFORM-3D software confirm that the constitutive model based on DRX softening effect has high accuracy in predicting the thermal deformation behavior of Ti-62A alloy in the dynamic recrystallization stage, which can provide technical reference for the actual production process. © 2020, Science Press. All right reserved.