Microstructures and mechanical properties of Mg–13Gd–5Er–1Zn–0.3Zr alloy

•The stacking faults precipitated on the basal plane in the as-cast alloy.•14H-LPSO structure grew from the stacking faults after homogenization treatment.•14H-LPSO structure and β’ phase coexist in the extruded alloy after aging treatment.•The UTS of the extruded alloy after ageing treatment was 410.9 MPa.

Microstructure and mechanical properties of the Mg–13Gd–5Er–1Zn–0.3Zr alloy were investigated by optimal microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS) and transmission electron microscopy (TEM) in the present investigation. The results suggested that the basal plane stacking faults (SF) of Mg crystal was present together with the precipitation of the (Mg,Zn)5(Gd,Er) phase. The parts of the (Mg,Zn)5(Gd,Er) precipitate were dissolved into the matrix during homogenization treatment at 733 K. In addition, a new kind of lamellar-shaped 14H long-period stacking-ordered (LPSO) structure was precipitated from the stacking faults of basal plane during homogenization treatment at 733 K. However, the unstable β′ phase was precipitated in the extruded grains after ageing treatment. The presence of both the 14H-LPSO structure and the β′ precipitate resulted in a great enhancement in mechanical properties. The values of the tensile yield strength and ultimate tensile strength were 338.8 MPa and 410.9 MPa, respectively.