Developing Improved Mechanical Property and Corrosion Resistance of Mg-9Li Alloy via Solid-Solution Treatment

Abstract

Cast Mg-9Li alloy was successfully solid-solution (SS) treated via heating at 575 °C for 4.5 h and rapidly quenched with ice-water mixture. The mechanical property and corrosion resistance of the SS alloy were simultaneously improved. Rapid bcc/hcp phase transition of the alloy occurred during the quenching process, creating the newly precipitated needle-like fine α-Mg phase, uniformly distributed in the β-Li phase matrix. Dramatic grain refinement and uniform distribution of the α-Mg phase, as well as the massively increased α/β phase interfaces, are factors leading to the improved mechanical property of the SS alloy. Meanwhile, due to the modified duplex-phase structure, the SS alloy has a uniform corrosion-resistant surface film on the β-Li phase, which completely covers the entire alloy surface and efficiently protects the substrate. In addition, the SS alloy has fewer difference in the elements concentration and corrosion activity of the duplex phases, which reduces the pitting sensitivity and improves the corrosion resistance of the alloy matrix. The findings in this binary Mg-Li alloy can also serve as a benchmark for other more practical and complicated Mg-Li alloys.