Variant selection of twins with low Schmid factors in cross grain boundary twin pairs in a magnesium alloy

Samples of magnesium AZ31 alloys are deformed in compression at room temperature under a strain rate of 1×10−3 s−1. The initial texture with respect to the loading direction is favorable for {10-12} extension twinning during the deformation. At an engineering strain of 2.75%, many extension twins are found to be connected with each other at grain boundaries, forming cross grain boundary twin pairs. Some have low positive or even negative Schmid factors (SFs). The variant selection of them are interpreted in terms of shear accommodations. The observed twin variants require the least or no accommodation through deformation modes with high CRSSs, but the most or more accommodation through those with low CRSSs.