Unraveling the effect of Zn and Ca additions on tensile properties and bendability of a new formable Mg-Al-Mn alloy sheet

This work aims to reveal the actual effect of Zn and Ca additions on tensile properties and bendability of a recently designed Mg-3Al-0.2Mn (mass%, AM30) sheet with high formability. We fabricated AM30 and Mg-3Al-0.8Zn-0.5Ca-0.2Mn (mass%, AZXM3100) sheets with weakly aligned (0001) poles. Their deformation behaviors were thoroughly investigated using electron backscattered diffraction and crystal plasticity simulation. We found that the Zn and Ca additions were not effective in improving the ductility and formability. Both the sheets showed large elongation to failure of ∼30% in tension, and their maximum bending angles during three-point bending were ∼90°. In-depth characterization of the deformation behaviors revealed that the Zn and Ca additions slightly facilitated tensile twinning, and the activity of the non-basal prismatic slip did not increase in the AZXM3100. Moreover, the Al₂Ca phase, which was formed in the AZXM3100, promoted the formation and propagation of cracks by concentrating plastic deformation. Therefore, ductility and formability could not be improved even after the Zn and Ca additions.