Microstructure and Mechanical Properties of As-Cast and Hot Extruded–Sheared ZG61 Alloy

In this study, the microstructural evolution and mechanical properties of as-cast and hot extrusion–shearing (HES) Mg-6Zn-1Gd-0.6Zr (ZG61) alloy were investigated under different strain rates. The experimental results illustrated obviously refine grains of the homogenized alloy after HES process from 325 to 7.6 μm. X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy (EDS) revealed the presence of Mg₃GdZn₆ phase and Mg₃Gd₂Zn₃ phase. ZG61 alloy illustrated a characteristic basal fiber texture (<0001> ⊥ ED), and the c-axes of grains were mostly perpendicular to the ED after HES process. The experimental results also illustrated that both of the tensile and compression mechanical properties enhance with increment of strain rate, showing the positive strain strengthening. Meanwhile, the mechanical characteristics such as ultimate tensile strength, yield strength, and elongation of HES ZG61 alloy improved by 70.8, 221.4, and 64.2% compared to the as-cast ZG61 alloy, respectively, due to grain refinement during hot extrusion process.