Use of Schmid factors to select extension twin variants in extruded magnesium alloy tubes

By analogy with dislocation glide, a Schmid factor criterion is often used in the case of twinning. The deformation textures of extruded AM30 magnesium alloy tubes deformed along different directions show clear evidence that extension twinning is responsible for the texture changes and that its activation is dictated by the Schmid factors applicable to different twinning planes. The rules for the selection of the twin variants in the present case are particularly well defined because of the sharp texture of the starting material.