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 = ε ̇ exp [ ( 933.3233 × 10 3 ) / 8.31 T ] / 6.17726 × 10 36 . 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 X DRX = 1 − exp { − [ ( ε − ε c / 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 ε c = 0.028774 ( Z / A ) 0.04665 , ε ⁎ = 0.45379 ( Z / A ) − 6.118274 e - 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.