Effect of Long-Period Stacking Ordered Phases on Dynamic Recrystallization Behavior of Mg-13Gd-4Y-2Zn-0.5Zr Alloy at Different Compression-Torsion Temperatures

The microstructure evolution of Mg-13Gd-4Y-2Zn-0.5Zr (wt.%) alloy with long-period stacking ordered (LPSO) phases after compression-torsion deformation (thereinafter referred to as CT deformation) at different temperatures was analyzed by optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) analysis, especially the evolution of LPSO phases during CT deformation. In addition, dynamic recrystallization (DRX) behavior during CT deformation and the impact of LPSO phase evolution on DRX behavior was explicated. The results showed the structures by order of appearance: lamellar LPSO phase (light kink—moderate kink—severe kink—almost no kink) and bulk LPSO phase (needle-like projections—tearing—dissolution—crushing) at increased CT deformation temperature. The proportion of DRXed grains gradually increased with CT deformation temperature, ranged from 11.6% at 350 °C to 40.9% at 480 °C. Apart from the increases in atomic thermal vibration and diffusion rate owing to increase in CT deformation temperature, the bulk LPSO phases at the grain boundary showed enhanced lattice rotation, which provided an ideal position for the nucleation of DRXed grains, and promoted the accumulation of strain gradient during deformation. Meanwhile, the second-phase particles distributed in the grain and grain boundary promoted DRX nucleation through PSN mechanism.