Microstructures and mechanical properties of Mg–10Gd–6Y–2Zn–0.6Zr(wt.%) alloy

• A high-strength Mg–10Gd–6Y–2Zn–0.6Zr alloy is prepared by conventional casting, extrusion and heat treatment techniques. • 6H-type long-period stacking order structure is identified in homogenized specimen. • The effect of LPSO structure on the mechanical properties of as-extruded Mg–10Gd–6Y–2Zn–0.6Zr alloy is discussed. • Strengthening models are considered to predict the tensile proof strength. • The calculated tensile proof strength partly agrees with the experimental tensile proof strength. Microstructures and tensile mechanical properties of Mg–10Gd–6Y–2Zn–0.6Zr alloy were systematically studied. Four phases were found in the as-cast specimen: α-Mg, Mg 3(GdYZn), Mg 12(GdY)Zn and Mg 24(GdYZn) 5. The long-period stacking order (LPSO) structure is found, which is the phase of Mg 12(GdY)Zn. The LPSO structure has two existing forms: lamellar structure in the inner grains and block-like structure at grain boundaries. 6H-type LPSO structure with a stacking sequence of ABCBCB′ is defined in homogenized specimen, where A and B′ layers are significantly enriched by Gd, Y and Zn. The ageing hardening behavior of as-extruded specimens at 200 °C has been investigated. The ultimate tensile strengths of the as-extruded and peak-aged alloys are 360 MPa and 432 MPa, and the elongations are 18% and 5% respectively. The effective strengthening models have been considered to predict the strength. The results suggested that the sub-micron metastable β′ phase was the main strengthening factor of the peak-aged alloy.