Effects of 0.5 wt% Ce addition on microstructures and mechanical properties of a wrought Mg−8Gd−1.2Zn−0.5Zr alloy

Effects of 0.5 wt% cerium (Ce) addition on microstructures and mechanical properties of a wrought Mg−8Gd−1.2Zn−0.5Zr alloy were thoroughly investigated in this work. The results indicate that 0.5 wt% Ce addition has slight refinement on the as-cast grains and results in a lattice expansion of the dominant intermetallic phase Mg3RE. After extrusion, 0.5 wt% Ce addition leads to higher level of recrystallization and finer dynamic recrystallization (DRX) grains and non-recrystallization stripes. In addition, there are much more dynamic precipitates on the DRX grain boundaries in the alloy with Ce addition, and the crystal structure (Mg12RE) is different from those (Mg5Gd) in the alloy with free Ce addition. Under peak-aging condition, 0.5 wt% Ce addition significantly changes the precipitates in the DRX grains from basal γ′ phase to prismatic β′ phase. As a result, the as-extruded Mg−8Gd−1.2Zn−0.5Zr alloy with 0.5 wt% Ce addition owns higher strength and more obvious precipitation hardening response than the alloy with free Ce addition.