An effective Schmid factor in consideration of combined normal and shear stresses for slip/twin variant selection of Mg-3Al-1Zn alloy

An effective Schmid factor (ESF), as an alternative parameter to the uniaxial stress based Schmid factor, is newly proposed to account for the effects of grain orientations and general loading conditions including shear deformation on the selection of slip/twin modes of magnesium alloys. The validity of the proposed parameter is confirmed by accurately predicting twin variants developed during double pass differential speed rolling of Mg-3Al-1Zn alloy. The analysis based on the ESF concept clarifies that shear stress and their relative magnitude to the normal stress have considerable impact on the activation of the predominate slip, twin type and variants.