Dynamic recrystallization kinetics in α phase of as-cast Ti-6Al-2Zr-1Mo-1V alloy during compression at different temperatures and strain rates

In order to evaluate the dynamic recrystallization (DRX) behavior of as-cast Ti-6Al-2Zr-1Mo-1V alloy, a series of compressions with a height reduction of 60% were performed in a temperature range of 1073-1323 K (0.55-0.68Tm) and a strain rate range of 0.01-10 s−1 on a Gleeble1500 thermo-mechanical simulator. By the regression analysis for conventional hyperbolic sine equation, the activation energy of DRX was determined as Q=933.3233 kJ mol−1, and a dimensionless parameter controlling the stored energy were determined as Z/A=ε̇exp[(933.3233×103)/8.31T]/6.17726×1036. According to the strain hardening rate curves (dσ/dε versus σ), three characteristic parameters including the critical strain for DRX initiation (εc), the strain for peak stress (εp), and the strain for maximum softening rate (ε⁎) were identified. A modified Avrami type equation XDRX=1−exp{−[(ε−εc/ε⁎)]m} was introduced to characterize the evolution of DRX volume fraction in α-phase temperatures under 0.59Tm, in which εc, ε⁎ and m were described as εc=0.028774(Z/A)0.04665,ε⁎=0.45379(Z/A)−6.118274e-4 and m=4.133402 respectively. The evolution of DRX volume was described as the following: for a fixed strain rate, the strain required for the same amount of DRX volume fraction increases with decreasing deformation temperature, in contrast, for a fixed temperature, it increases with increasing strain rate. Finally, the theoretical predictions were validated by the microstructure graphs.