Investigation on the Grain Structure Evolution and Abnormal Stress Increase of Al–Mg–Si Alloy During Hot Deformation

Al–Mg–Si alloys are widely used in many fields due to their excellent comprehensive performance, but medium strength. In order to study the hot deformation behavior and microstructural evolution of Al–Mg–Si alloys, the isothermal compression tests were carried out on the Gleeble-3500 thermal/mechanical simulation machine. The varying temperatures between 623 and 773 K and strain rates of 0.001 s⁻¹ to 1 s⁻¹ with true strain of 0.51, 0.92 and 1.2 were considered. Strain-compensated Arrhenius model with modified friction was constructed and the correlation coefficient (R), absolute relative error (AARE) between the experimental and predicted values reached to 0.998 and 1.95%. The results showed that, the critical stress (σ_c) of recrystallization was reduced with increase in temperature and decreased strain rate. The softening mechanism by dynamic recrystallization (DRX) was enhanced with the existence of dynamic recovery (DRV) and different DRX behaviors with different mechanisms were identified and discussed. From the analysis of the microstructure after the friction was excluded, it was observed that the texture was enhanced with large deformation with increased dislocation density. The strain hardening effect of deformation was stronger than the dynamic softening which led to the abnormal increase of stress. Graphical Abstract: (Figure presented.).