Evolution of LPSO Phases and Their Effect on Dynamic Recrystallization in a Mg-Gd-Y-Zn-Zr Alloy

The effect of long-period stacking ordered (LPSO) phases on the dynamic recrystallization (DRX) of the compressed Mg-6.9Gd-3.2Y-1.5Zn-0.5Zr (wt pct) alloy was investigated. LPSO phases of various morphologies were obtained by homogenization at 783 K (510 A degrees C) for various durations. During homogenization, intragranular thin-platelet LPSO phases form near the alpha-Mg grain boundaries first, then penetrate through the grain interior, and finally coagulate. During compression at 753 K (480 A degrees C), intragranular thin-platelet LPSO phases reduce the DRX ratio by hindering the migration of alpha-Mg grain boundaries. Intragranular-coagulated LPSO phases stimulate DRX near the alpha-Mg grain boundaries, while faintly affecting the DRX behavior in the interior of alpha-Mg grains. However, interdendritic phases enhance the nucleation of DRX-ed grains via the particle-stimulated nucleation mechanism. Among all the compressed alloys, the alloy rich in thin-platelet LPSO phases exhibits the optimal mechanical properties.