Effect of rolling speed on microstructure and mechanical properties of as-cast AZ31B alloy under different reduction schedules

AZ31B alloy was severely rolled at speeds between 18 and 102 m/min by two different reduction schedules, respectively. The recrystallization behaviors, rolling feasibility, temperature distribution, texture and mechanical properties were examined. The {10 1 ¯ 2} tensile twinning and subsequent secondary twinning and continuous dynamic recrystallization dominated the deformation. For 4-pass rolling, as the speed increased, the twin density gradually decreased and the grain size slightly rose due to the suppressed temperature reduction at higher speed. However the effective grain size sharply increased and the recrystallization fraction dropped with increased rolling speed for 2-pass rolling. Full recrystallization mainly occurred in grains with beneficial orientations for {10 1 ¯ 2} twinning, rather than dislocation, during 2-pass rolling at speeds higher than 72 m/min. The rolling feasibility, texture and mechanical properties were largely affected by rolling speed. However, their trends were significantly different, sometimes even on the contrary, under different reduction schedules.