Effect of crystal orientation on the mechanical properties and strain hardening behavior of magnesium alloy AZ31 during uniaxial compression

The effect of initial texture on the mechanical properties and strain hardening behavior of AZ31 magnesium alloy has been investigated. Cylindrical specimens of extruded and hot rolled AZ31 are compressed along different directions, with the compression axis (C) perpendicular or parallel to the extrusion direction (ED) or the sheet normal direction (ND), referred to as C⊥ED, C//ED, C⊥ND and C//ND specimen, respectively. The compression tests are conducted at room temperature with a strain rate of 0.01 s−1. The results indicate that the yield strength and the strain hardening rate are highly anisotropic with respect to the initial texture. The significant yield behavior can be induced by only a small volume of twins. When the initial grain orientations are unfavorable for {101¯2} twinning, the strain hardening rate decreases gradually. When the initial grain orientations are favorable for {101¯2} twinning, the strain hardening behavior exhibits three distinct stages. The main contribution to increasing strain hardening rate (corresponding to the stage II) results from texture strengthening, which rotates grain orientations into hard orientations by the {101¯2} twinning. The length of the stage II is predominantly related to the volume fraction of grains which are favorable for {101¯2} twinning.

► Stage II strain length determined by the amount of grains favorable for twinning.
► Contribution to increasing strain hardening rate results from texture strengthening.
► Significant yield behavior can be induced by only a small amount of twins.