Crystallographic analysis on the activation of multiple twins in rolled AZ31 Mg alloy sheets during uniaxial and plane strain compression

It is well known that the activation and interception of multiple twins in Mg alloys largely influence microstructural evolution and strain hardening behavior. However, the crystallographic conditions for the activation of multiple twins and their variant selection have not been well understood. Therefore, the present work was conducted in attempt to find some trends such as grain orientation, Schmid factor and geometric compatibility factor on the activation and variant selection of multiple twins in both uniaxial compression (UC) and plane strain compression (PSC). The results showed that most of the twins in single twin grains strictly followed Schmid law. For the activation of multiple twin variants inside grains and cross-boundary twins, the local strain compatibility between the connected twins was also important for variant selection. Because of the constraint along the c-axis, twinning activation was suppressed in PSC compared to UC. In general, the variant selection of twinning was more likely affected by local strain compatibility in PSC than that in UC. These experimental results may shed light on the development of advanced physics-based simulation models.