Dynamic microstructure evolution and mechanical properties of dilute Mg-Al-Ca-Mn alloy during hot rolling

• The microstructure evolution of AXM050703 alloy were systematically studied. • The interaction of {10-12} twins, {10-11} - {10-12} twins and kinks were studied. • The Multi-pass rolling samples with different microstructures were prepared. • The strength of these alloy (alloying elements only 1.5 wt.%) is higher than AZ31B. The dynamic microstructure and texture of dilute Mg-0.50Al-0.71Ca-0.33Mn (wt.%) during hot rolling at two slab temperatures were investigated by electron backscattered diffraction (EBSD) and high resolution transmission electron microscopy (HRTEM). The results show that the development of the rolling microstructures is to first form {10-12} extension twins in the original grains, thereby forming the extension-twinned regions, and then further form {10-11} - {10-12} double twins and kinks in the extension-twinned regions, and finally form continuous dynamic recrystallized (continuous DRXed) grains in the double twins and the cross parts of the shear-deformed coarse extension-twinned regions. These extension twins, double twins and kinks show a decisive effect on the formation of rolling texture. Because the number of {10-11} - {10-12} double twins and the continuous DRX process are strongly affected by the rolling slab temperature and the reduction thickness per pass, the authors successfully modified the texture and the microstructures of the multi-pass rolled Mg-Al-Ca-Mn alloy sheets by optimizing the rolling conditions. Although the total alloy element is only 1.5 wt.%, these Mg-Al-Ca-Mn alloy sheets show much higher strength than the commercial Mg-3Al-1Zn (wt.%) (AZ31B) sheet.