Nanostructured extension twins in rapidly compressed Mg–3.0Al–1.0Zn alloy

Magnesium alloy components are potentially subjected to dynamic strain rate loading. High strain rate usually results in a mechanical behavior quite different from that under quasi-static loading. In the present study, twin characteristics were investigated in Mg–3.0Al–1.0Zn (AZ31B) alloy compressed at dynamic strain rate of 8.0×10−1 s−1. In addition to large extension twins, nanostructured lamella extension twins were found in a large number in the matrix. The reason that such nanostructured twins co-exist with large twins was explained in terms of comparison between dislocation and twinning dynamics, i.e., due to the high strain rate, the dynamic critical resolved shear stress for slip could be so high as to result in a viscous drag and the abundant occurrence of the rapid shear of the extension twinning should be needed in widely oriented grains to accommodate strain.