Kinetic analysis and strain-compensated constitutive models of Ti-42.9Al-4.6Nb-2Cr during isothermal compression

The hot deformation behavior of Ti-42.9Al-4.6Nb-2Cr (at. %) was investigated by isothermal compression tests at the deformation temperature range of 1373-1573 K, strain rate range of 0.001-1.0 s(-1), up to the strain of 0.69. The flow stress test results of Ti-42.9Al-4.6Nb-2Cr showed negative temperature and positive strain rate sensitivity. Besides, strain had a great effect on the hot deformation behavior of Ti-42.9Al-4.6Nb-2Cr. Kinetic analysis was adopted to assess the hot workability of Ti-42.9Al-4.6Nb-2Cr via apparent activation energy (Q) of hot deformation, strain-rate sensitivity index (m) and strain hardening index (n). The Q value varied from 607.1 +/- 0.7 kJ.mol(-1) to 512.6 +/- 10.8 kJ mol(-1) with the increasing of strain from 0.1 to 0.6. The effect of strain on the Q value at the deformation temperatures below 1473 K was mainly related to dynamic recrystallization of gamma phase and kinking of gamma lamellae, while the Q value at the deformation temperature above 1473 K might be linked to gamma ->infinity phase transformation and DRV of a phase. Based on the kinetic analysis, strain-compensated Arrhenius model and Hensel-Spittel model were successfully established to predict the hot workability (flow stress). Average absolute relative errors of established strain-compensated Arrhenius model and Hensel-Spittel model were 7.52% and 11.95%, respectively. Moreover, both established constitutive models can be extrapolated for predicting the flow stress of Ti-42.9Al-4.6Nb-2Cr to larger strain levels.