A cross-shear deformation for optimizing the strength and ductility of AZ31 magnesium alloys

Magnesium alloys have recently attracted great interest due their lightweight and high specific strength. However, because of their hexagonal close-packed structure, they have few active slip systems, resulting in poor ductility and high mechanical anisotropy at room temperature. In the present work, we used a cross-shear deformation imposed by a differential speed rolling (DSR) technique to improve the room temperature strength and ductility of AZ31 magnesium alloy sheets. To introduce the cross-shear deformation, the sheets were rotated 180 degrees around their longitudinal axis between the adjacent passes of DSR. The sheets of the AZ31 alloy subjected to the cross-shear deformation showed a uniform fine microstructure (1.2 +/- 0.1 mu m) with weak basal textures. The fabricated sheets showed a simultaneous high ultimate tensile strength and elongation-to-failure, i.e., similar to 333 MPa and similar to 21%, respectively. These were explained based on the structural features evolved due to the cross-shear deformation by DSR. The high strength was attributed to the uniform fine microstructure, whereas the high ductility was explained based on the basal texture weakening.