Modeling the microstructure evolution in AZ31 magnesium alloys during hot rolling

A new model was proposed based on the dislocation density of the computer simulation of the microstructure evolution in magnesium alloys. It is possible to describe the continuous dynamic recrystallization (CDRX) interaction including work-hardening, dynamic recrystallization (DRX) and dynamic recovery (DRV) changing with rolling time. The transient hot rolling simulation was performed by implementing this model under various rolling temperatures and strain conditions using the finite diffraction method (FDM). Normal rolling experiments were conducted at different reductions and starting rolling temperatures. Microstructural parameters, such as grain size, subgrain size, misorientation angle, high-angle grain boundary (HAGB), and low-angle grain boundary (LAGB), were measured using electron back-scattering diffraction (EBSD). The dislocation density of LAGB and the hypothetical dislocation density of HAGB were estimated through theoretical derivation using the experimental data. As a result, changes in the hypothetical dislocation density of HAGB and the dislocation density of LAGB of the model prediction fit well with the experimental data. The microstructure evolution mechanisms of the AZ31 magnesium alloy in the roll bite were examined at 300, 400 and 500 °C rolling. As a result, it is clear that the work-hardening is a dominated mechanism of 300 °C rolling in the rolling strain ranging from 0 to 0.6. However, the DRV plays a vital role in the microstructure evolution at 400 and 500 °C rolling.