Dependence of Microstructure Evolution and Mechanical Properties on Loading Direction for AZ31 Magnesium Alloy Sheet with Non-basal Texture During In-Plane Uniaxial Tension

Abstract

In-plane uniaxial tension of AZ31 magnesium alloy sheet with non-basal texture has been conducted in order to demonstrate the effects of loading direction on the microstructure evolution and mechanical properties at ambient temperature. Loading axes are chosen to be along five directions distributed between rolling direction (RD) and transverse direction (TD), allowing various activities in involved slip and twinning modes to take place. As for twinning modes, electron backscattered diffraction observations confirm that the contribution of ${{\{ 10\overline{1}1\} }}$ compression twinning is minimal to the plastic deformation of all deformed samples. By comparison, ${{\{ 10\overline{1}2\} }}$ extension twinning (ET) not only serves as an important carrier on sustaining and accommodating plastic strain but also contributes to the emergence of TD-component texture with the progression of plastic strain. In terms of slip modes, analysis on Schmid factor demonstrates that the increasing tilted angle between loading direction and RD of sheet is unfavorable to the activation of basal <a> slip, whereas it contributes to the activation of prismatic <a> slip. These observations consequently explain the increasing tendency of 0.2% proof yield stress. Moreover, the activations of basal <a> slip and ${{\{ 10\overline{1}2\} }}$ ET collectively contribute to the concentration of two tilted basal poles toward normal direction. With increasing angle between loading direction and RD, the activations of basal <a> slip and ${{\{ 10\overline{1}2\} }}$ ET are gradually weakened. This leads to a weakening tendency about concentration of two tilted basal poles, a generally increasing tendency about Lankford value (r-value) and a generally decreasing tendency about strain-hardening exponent (n-value).