Microstructure evolution and mechanical properties of the Mg-Sm-Gd-Zn-Zr alloy during extrusion

Abstract Mg-2.6Sm-1.3Gd-0.6Zn-0.5Zr (wt.%) alloy is prepared with metal mold casting and followed hot extruded at 400°C with the extrusion ratio of 25:1. Microstructure and mechanical properties of the as-extruded alloy are investigated using optical microscope (OM), scanning electron microscope (SEM) with electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that the as-extruded alloy is fully dynamically recrystallized, which develops rare earth (RE) texture component. The as-extruded alloy shows an age-hardening response at 200°C, in which there are numerous nano-scale plate strengthening phase β′ precipitated in the matrix. The as-extruded alloy in the peak-aged condition exhibits ultimate tensile strength, yield strength, and elongation of 332 MPa, 220 MPa and 22.7% at room temperature, respectively. The dominant strengthening mechanisms of the investigated alloy are fine-grain strengthening, solid solution strengthening and precipitate strengthening.