Hot deformation behavior and microstructure evolution of Ti-6Cr-5Mo-5V-4Al alloy during hot compression

The true stress strain curves of Ti-6Cr-5Mo-5V-4Al alloy at the deformation condition range of 963-1113 K & 0.001-1 s(-1) were acquired by hot compression tests carried out on a Gleeble-3500 isothermal simulator. The higher softening values in the alpha + beta phase field reveal the occurrences of dynamic recrystallization (DRX) and dynamic globularization (DG), and the lower softening values in the beta phase field reveal that dynamic recovery (DRV) predominates. The constitutive relationships of this alloy in alpha + beta phase field and beta phase field were developed based on an improved Arrhenius model. The strain rate sensitivities (m) were determined and the temperature sensitivities (theta) were calculated by a modified function. The stacking contour map consisted of temperature sensitivity, strain rate sensitivity and microstructures at the strain of 0.9 was developed. By comparing the relationship between the three factors, the deformation defects are risky to occur at the deformation condition with high theta-value (> 0.5) and low m-value (< 0.17) and reasonable microstructure could be obtained at the condition with low theta-value (< 0.4) and reasonable m-value (> 0.2). Based on the obtained criterions, an optimal working area map was constructed, which is beneficial for intrinsic hot workability identification for this alloy.