A strategy for mitigating mechanical anisotropy of GWZ932 Mg alloy via cryogenic-annealing cyclic treatment

Mechanical anisotropy remains a fundamental barrier to the widespread applications of Mg alloys. In this study, a cryogenic-annealing cyclic (CAC) process was proposed to mitigate the mechanical anisotropy of the GWZ932 Mg alloy through multi-scale microstructural modulation. Cryogenic exposure introduces a high concentration of excess vacancies and promotes dislocation proliferation, which provides rapid atomic diffusion pathways and accumulates the internal stress for subsequent annealing. Afterwards, the dynamic equilibrium between dislocation multiplication and annihilation is established through the recovery during annealing. In addition, CAC process induces pronounced morphological refinement of 18R-LPSO phases, and facilitates the homogeneous precipitation of Mg 3 RE and RE-rich phases along the grain boundaries. Moreover, the enhanced co-segregation of Gd and Zn at grain boundaries reduces the critical resolved shear stress for non-basal slip activation. The combined effects of internal stress and thermal activation facilitate the static recrystallization, accompanied by a pronounced adjustment of crystallographic c -axis distribution. As a result, CAC process minimizes the variation in yield strength, ultimate tensile strength, and elongation across different loading directions. This fundamentally transforms the mechanical response from highly anisotropic to quasi-isotropic, attributed to enhanced non-basal slip activation and improved deformation compatibility among the grains with diverse orientations.