Effect of annealing on microstructure and mechanical properties of ZK60 magnesium alloy sheets processed by twin-roll cast and differential speed rolling

In this study, ZK60 magnesium strips produced by twin-roll casting were subjected to differential speed rolling with velocity ratios of 1.2 and 1.5 and equal speed rolling. Annealing treatment was applied to the rolled strips to investigate its effect on microstructure, texture and mechanical properties. The results show that compared with the sheet processed by equal speed rolling, the sheets processed by differential speed rolling show more apparent shear bands in the rolled state and a higher fraction of fine grains after annealing. The sheets processed by differential speed rolling show a single-peak basal fiber with a decreased maximum pole intensity compared to a clear double-peak texture of the sheet processed by equal speed rolling, and both are weakened after annealing. The sheets processed by differential speed rolling present significantly higher ductility and slightly lower yield strength than the sheet processed by equal speed rolling. The annealing process contributes to decreases in the strengths and improvement in ductility, which can be attributed to the weakening of basal texture by recrystallization. These results suggest that the annealing is an effective way to enhance the formability of sheets produced by differential speed rolling.