Crystal Plasticity Finite Element Modeling of Grain Size Influence on Tension–Compression Asymmetry in Extruded Magnesium Alloys

Magnesium alloys have attracted increasing attention as lightweight structural materials for transportation and energy industries; however, their applications remain limited by pronounced tension–compression yield asymmetry and low ductility. In this work, the influence of grain size on the mechanical behavior of extruded Mg–XY (X = ۰–۳ wt%) alloys was investigated using a three-dimensional crystal plasticity finite element model. A representative volume element (RVE) was developed to simulate the grain-scale deformation mechanisms under uniaxial tension and compression along the extrusion direction. The model incorporated multiple slip and twinning systems to capture the anisotropic response of the alloys. The simulations revealed a strong dependence of yield strength and strain-hardening behavior on grain size. Reducing the grain size from ۵۰ μm to ۷ μm significantly increased both tensile and compressive yield strengths while decreasing tension–compression yield asymmetry. The enhanced mechanical performance was attributed to the suppression of tensile twinning and increased activation of non-basal slip, which promote a more homogeneous deformation. Furthermore, finer grains exhibited a two-stage hardening response with higher strain-hardening capacity compared to coarse-grained alloys. Overall, the findings demonstrate that microstructural refinement is an effective approach for improving the strength, hardening behavior, and mechanical symmetry of extruded Mg–RE alloys. This study provides valuable insight into the grain-size–dependent deformation mechanisms and offers practical guidance for designing lightweight magnesium components with superior mechanical reliability.

کلیدواژه ها:

Grain size ، Mg alloys ، Crystal plasticity ، Finite element modeling ، Slip–twinning ، Tension–compression asymmetry