The mechanism for the different effects of texture on yield strength and hardness of Mg alloys

A study regarding the effect of texture on tensile yield strength and hardness of an extruded Mg-15Gd-0.5Zr rod was performed, with a great emphasis laid on the relevant mechanisms. A 7% pre-tension along the extrusion direction (ED) in the solid solution condition was used to transform the texture from a broad distribution of basal poles with a peak approximately 45° with respect to the ED into a texture with basal poles largely perpendicular to the ED. This texture variation enhances the yield strength of peak aged sample by approximately 103 MPa, while hardly increases the peak hardness. The analysis about the ratio of the critical resolved shear stress (CRSS) to Schmid factor shows that this texture variation results in a larger fraction of grains favoring prismatic slip with a higher activation stress under tension along the ED. In contrast, the complex stress state during hardness test initiates multiple deformation modes, which renders the value of hardness insensitive to the texture variation. This different dependence of deformation modes on texture mainly accounts for the different increments in hardness and tensile yield strength.