Continuous dynamic recrystallization behavior and kinetics of Al-Mg-Si alloy modified with CaO-added Mg

Hot torsion tests were performed on an Al-Mg-Si alloy modified with CaO-added Mg to investigate the effect of a novel Mg additive with improved oxidation resistance on the hot deformation and dynamic recrystallization (DRX) behavior. The features of the flow curves and deformed microstructure indicated that continuous dynamic recrystallization (CDRX) was a major restoration mechanism of the alloy. The flow curves demonstrated that the failure strain of the modified alloy was greater than that of the conventional alloy. The deformed microstructure, which was studied by electron backscatter diffraction (EBSD), revealed that the CDRX was initiated at a lower strain for the modified alloy. The CDRX fraction of the modified alloy was greater than that of the conventional alloy. The increased failure strain and greater CDRX fraction were primarily attributed to differences in the amount and distribution of second phase particles, which were derived from the improved oxidation resistance of the CaO-added Mg. In addition, a kinetic model for the CDRX was proposed, which corresponded well with the experimental data.