Effect of Y on microstructure and mechanical properties of duplex Mg–7Li alloys

Mg–7Li–xY (x = 0–7 wt.%) alloys were prepared by permanent mould casting method, and the microstructure and mechanical properties of the alloys were investigated. The results show that α-Mg and β-Li phases exist in all alloys. The Y-enriched α-Mg phase distributes along the edge of α-Mg phase and in the β matrix of x = 1–7 alloys, and Mg24Y5 mainly disperses in the β matrix of x = 3–7 alloys. The strength of the alloy is enhanced by adding Y element, and the elongation is improved with the Y content no more than 3 wt.%. The as-cast Mg–7Li–3Y alloy exhibits an optimum combination of mechanical properties with the ultimate tensile strength, yield strength and elongation of 160 MPa, 144 MPa and 22%, respectively. After solutionized at 400 °C for 3 h with a subsequent aging at 100 °C, Mg–7Li–7Y alloy exhibits high ultimate tensile strength and yield strength, which are improved to 120% and 152% compared with those of the as-cast Mg–7Li alloy, respectively.

Research highlights▶ This work has studied the microstructure and mechanical properties of the as-cast duplex Mg–7Li–xY alloys with the Y content from 0 wt.% to 7 wt.%. ▶ The microstructure and mechanical properties of the T4 and T6 heat-treated duplex Mg–7Li–1Y and Mg–7Li–7Y alloys were also studied. ▶ The solubility of Y element in the Li-based phase has been studied.