Evolution of LPSO Phase in Hot Deformation of as-Forged Mg-9Gd-3Y-2Zn-0.3Zr Alloy and its Effect on Microstructure and Recrystallization Mechanism

In this article, the hot deformation behavior of as-forged Mg-9Gd-3Y-2Zn-0.3Zr alloy is investigated by using Gleeble 3500 thermomechanical simulation under 350–500 °C, strain rates of 0.01–10 s⁻¹, and 60% deformation. The evolution of long period stacking ordered (LPSO) phases and their effects on microstructure and dynamic recrystallization (DRX) mechanisms are systematically explored. The results show that the flow behavior is strain-rate-sensitive, transitioning from dynamic recovery (<0.1 s⁻¹) to DRX (>0.1 s⁻¹). The LPSO phases flatten and fragment during deformation, with fragmentation increasing at higher strain rates (0.01 → 10 s⁻¹), causing volume fraction to first decrease (12.5% → 8.6%) then rise (17.2%). At 1 s⁻¹, higher temperatures (400 → 500 °C) lead to LPSO aggregation, with volume fraction peaking at 14.1%. LPSO phases promote DRX via particle-stimulated nucleation and kink-induced continuous DRX. Optimal grain uniformity (2.21 μm) occurs at 400 °C/1 s⁻¹ with 8.6% LPSO. The findings reveal LPSO's role in microstructure modulation, aiding high-strength magnesium alloy design.