Effect of microstructure evolution on mechanical property of extruded Mg–12Gd–2Er–1Zn–0.6Zr alloys

The microstructure evolution of as-cast, as-extruded and peak-aged Mg–12Gd–2Er–1Zn–0.6Zr alloys were investigated by Optical Microscope (OM), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The mechanical performance was also tested by tensile test at room temperature in the present study. The results indicated that the lamellar 14H-LPSO structure formed during the solid solution process at 793 K for 24 h, and also existed after hot extrusion process. The dynamic recrystallization (DRX) occurred during hot extrusion. The DRXed fine grain size was ∼5 μm. Meanwhile, some un-DRXed grains contained LPSO structure had a roughly orientation along the extrusion direction. The tensile test result showed that the as-extruded alloy had a better elongation of 14% due to fine DRXed grain and fiber-like un-DRXed with LPSO structure attributed to the high elongation. Because of the precipitation of the β′-phase, the ultimate tensile strength (UTS) and yield tensile strength (YTS) increased up to 415 MPa (UTS) and 374 MPa (YTS), respectively.