Shear stress derived enhancement of LPSO deformation and DRX behavior for Mg-11Gd-4Y-2Zn-0.5Zr alloy

Mg-11Gd-4Y-2Zn-0.5Zr alloy with long-period stacking ordered (LPSO) phases exhibits excellent high-temperature strength and ductility. In this paper, the influence of compressive stress (hot compression) and shear stress (hot torsion) on the deformation of LPSO phases and dynamic recrystallization (DRX) behavior was investigated at 450 °C and 0.01 s −1 . Microstructural evolution was characterized using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD). The results revealed distinct stress-mode dependencies: DRX area fractions were notably higher under shear stress than under compressive stress. Moreover, the LPSO phases exhibited noticeably different deformation behaviors: intragranular lamellar LPSO phases exhibited weaker kinking deformation with lower kink angles during torsion, while intergranular block LPSO phases suffered more severe fragmentation under shear stress. Theoretical analysis confirmed that the enhanced fragmentation under torsion promotes DRX via particle-stimulated nucleation (PSN) mechanism. Analysis of in-grain misorientation axes (IGMA) and effective Schmid factors (ESF) demonstrated that more pyramidal < c + a > II slips were preferentially activated under shear stress. Such increased activation of pyramidal < c + a > II slip facilitates DRX nucle a tion by generating a higher density of low-angle grain boundaries and sub-grains compared to that under compressive stress.