Constitutive Modeling and Dynamic Recrystallization Mechanisms of an Ultralow-carbon Microalloyed Steel During Hot Compression Tests

The hot deformation behavior of an ultralow-carbon microalloyed steel was investigated using an MMS-200 thermal simulation test machine in a temperature range of 1 073–1 373 K and strain rate range of 0.01–10 s −1 . The results show that the flow stress decreases with increasing deformation temperature or decreasing strain rate. The strain-compensated constitutive model based on the Arrhenius equation for this steel was established using the true stress-strain data obtained from a hot compression test. Furthermore, a new constitutive model based on the Z -parameter was proposed for this steel. The predictive ability of two constitutive models was compared with statistical measures. The results indicate the new constitutive model based on the Z -parameter can more accurately predict the flow stress of an ultralow-carbon microalloyed steel during hot deformation. The dynamic recrystallization (DRX) nucleation mechanism at different deformation temperatures was observed and analyzed by transmission electron microscopy (TEM), and strain-induced grain boundary migration was observed at 1 373 K/0.01 s −1 .