Mechanical anisotropy due to twinning in an extruded AZ31 Mg alloy

Tensile and compressive tests were performed at room temperature −673 K on extruded AZ31 alloy specimens with different (0 0 0 2) texture intensities and grain sizes, and effects of the temperature, grain size and texture on the tensile-compressive anisotropy were investigated. The mechanical anisotropy was closely related to generation of {1 0 1¯ 2}〈1 0 1¯ 1〉 twin. The mechanical anisotropy decreased with increasing temperature because the difference in twin generation between the tensile and compressive tests was reduced at elevated temperature. The (0 0 0 2) texture affected the mechanical anisotropy because the twin generation was enhanced during the compressive tests when the (0 0 0 2) plane was distributed parallel to the compressive direction. Also, because the twin generation was suppressed by grain refinement, the mechanical anisotropy was reduced by grain refinement. This suggests that the grain size dependence of the twinning is larger than that of the slip operation.