The influence of intergranular misorientation on the deformation mechanisms and mechanical properties of pure magnesium

Grain orientation and intergranular misorientation are two key factors affecting the deformation behavior of magnesium (Mg). Previous extensive studies have proven that grain orientation determines the magnitude of the resolved shear stress of external loading acting on grains. However, the influence of intergranular misorientation on the deformation mechanisms and mechanical properties of Mg is still unclear. In this work, the Mg-sheet and Mg-rod with similar grain size but distinct intergranular misorientation distribution were selected as the study materials. The identical loading path, tension perpendicular to the c-axis of most grains, was applied to them. However, they showed similar yield strength but distinct ductility. The elongation of the Mg-rod was almost three times that of the Mg-sheet. Statistical slip trace analysis indicated prismatic slip and pyramidal slip exhibited much higher activity in the Mg-rod. The quantitative relationship between the geometric compatibility factor (m’) for various slip transfer types and the grain boundary misorientation angle (GBMA) has been established. It indicated (32°∼72°) and (72°∼90°) GBMA were in favor of the activation of pyramidal slip and prismatic slip, respectively. Accordingly, the uniform distribution of GBMA in the Mg-rod is the key factor for the higher activity of non-basal slip while GBMA clustering at (10°∼32°) in the Mg-sheet is not conducive to the startup of non-basal slip. The higher activity of non-basal slip results in the significantly superior ductility of the Mg-rod. The similar Schmid factor (SF) values for various deformation mechanisms keep the strength of the Mg-rod comparable to the Mg-sheet. Accordingly, tailoring intergranular misorientation can serve as a novel design concept for developing high-strength and high-ductility Mg alloys.