Microstructural characteristics of magnesium alloy sheets subjected to high-speed rolling and their rolling temperature dependence

Microstructural and textural variations of an AZ31 Mg alloy during its high-speed rolling (HSR) and their dependence on the rolling temperature are investigated by performing HSR at temperatures of 300 °C, 350 °C, and 400 °C at a rolling speed of 470 m/min with 80% reduction in a single pass. Shear band formation is observed in all the high-speed-rolled (HSRed) materials; however, with increasing rolling temperature, the density and intensity of the shear bands decrease considerably because of an increase in deformation homogeneity. With increasing rolling temperature, the area fraction of dynamically recrystallized (DRXed) grains gradually increases owing to the promoted twinning-induced recrystallization behavior. With an increase in the rolling temperature from 300 °C to 350 °C, the average grain size of the HSRed materials decreases owing to the reduced area fraction of coarse unDRXed grains; however, at 400 °C, the average grain size increases owing to the increased DRXed grain size. With decreasing rolling temperature, the basal texture of the HSRed materials tilts from the normal direction toward the rolling direction, owing to the intensive shear deformation at lower temperatures. The texture intensity also increases with decreasing rolling temperature because of an increase in the area fraction of the unDRXed region, which has a considerably strong texture.