Microstructural evolution during hot shear deformation of an extruded fine-grained Mg–Gd–Y–Zr alloy

Mg–Gd–Y–Zr alloys are among recently developed Mg alloys having superior mechanical properties at elevated temperatures. Dynamic recrystallization (DRX) and rare earth-rich particles play important roles in enhancing the high-temperature strength of these alloys. Accordingly, the microstructural evolution of a fine-grained extruded Mg–5Gd–4Y–0.4Zr alloy was investigated after hot shear deformation in the temperature range of 350–450 °C using the shear punch testing (SPT) method. The results reveal the occurrence of partial dynamic recrystallization at the grain boundaries at 350 °C while the fraction of DRX grains increases with increasing deformation temperature. A fully recrystallized microstructure was achieved after SPT at 450 °C. The Gd-rich and Y-rich cuboid particles, having typical sizes in the range of ~50 nm to ~3 μm, show excellent stability and compatibility after hot shear deformation, and these particles enhance the high-temperature strength during hot deformation at elevated temperatures. The textural evolution, examined using electron backscattered diffraction, revealed a non-fibrous basal DRX texture after SPT which is different from the conventional deformation texture.