A quantitative study on mechanical behavior of Mg alloys with bimodal texture components

The mechanical and twinning behavior of Mg alloys containing a monolithic texture component have been extensively studied; however, studies on samples with multi texture components are much insufficient. In this study, the quantitative relationship between the mechanical behavior under tension along the extrusion direction (ED) of Mg AZ31 rods and the percentages of bimodal texture components <0002>// ED (19–87%) and <0002>⊥ED were systematically studied. The component <0002>// ED favors { 10 1 ¯ 2 } twinning and is soft orientation; however, the component <0002>⊥ED favors prismatic slip and is hard orientation. The results show that the yield strength does not decrease linearly with an increase in the percentage of the soft orientations and show a deviation from the calculations using the conventional rule of mixtures. A higher percentage of the soft grains increases this deviation when the percentage is below 50%, and decreases it over 50%. The ultimate strengths, however, do not show an obvious dependence on the percentage of the soft orientations. Subsequently, the corresponding mechanisms are discussed and a modified rule of mixtures was developed. Bimodal texture components stimulate the activation of { 10 1 ¯ 2 } twin variants with a low Schmid factor and the presence of more variants within one grain. Conventional strain accommodation rule was used to analyze this twinning behavior, but it cannot explain the experimental observations. Crystal-plasticity based finite element modeling was employed to analyze this strange twinning behavior. The results indicate that the interaction among twin variants, rather than deformation in neighboring grains, plays a major role in the activation of twins with a low Schmid factor, due to a hard deformation propagation from the soft grains to the hard grains. This finding provides an important complementation to the strain accommodation theory.