Variation in Crystallographic Orientation and Twinning Activation with Size of Individual Grains in Rolled Magnesium Alloy

This study demonstrates that the size of an individual grain in a rolled AZ31 alloy is significantly related to the crystallographic orientation of the grain and the area fraction of the {10–12} twinned region formed in the grain after compression along the rolling direction. With an increase in the size of an individual grain from 11 μm to 80 μm, the angle between the c-axis of the grain and the normal direction of rolling plane decreases from 38° to 5.5° and the Schmid factor for {10–12} twinning of the grain increases from 0.29 to 0.5. As a result, the area fraction of the twinned region formed in the grain increases from 30% to 100% owing to the combined effect of an increase in the Schmid factor value and a decrease in the stress required for activation of twinning by the increased grain size. The grain size (GS), Schmid factor for {10–12} twinning (SF_twin), and twin fraction (TF) have the relation TF/SF_twin = 109.8 + 1.45GS.