Initiation and strain compatibility of connected extension twins in AZ31 magnesium alloy at high temperature

Uniaxial compression tests were carried out at 350 °C and a strain rate of 0.3 s− 1 on as-extruded AZ31 magnesium alloy samples. At a true strain of − 0.1, extension twin pairs in a grain and twin chains across adjacent grains were detected. The orientation of selected twins and their host grains were determined by electron backscattered diffraction (EBSD) techniques. The Schmid factors (SFs), accommodation strains and geometric compatibility factors (m′) were calculated. Analysis of the data indicated that the formation of twin pair and twin chain was related to the SF and m′. Regarding to twin chain across adjacent grains, accommodation strain was also involved. The selection of twin variants in twin chain was generally determined by m′. When the twins required the operation of pyramidal slip or twinning in adjacent grain, the corresponding connected twins with a relative high m′ were selected in this adjacent grain.