Microstructure and Hardness of Mg – 9Li – 6Al Alloy After Different Variants of Solid Solution Treatment

Abstract

The microstructure and the hardness of cast magnesium alloy Mg – 9% Li – 6% Al are studied after a treatment for solid solution at 300, 350, and 450°C for 0.5 – 5 h. The phase composition of the alloy is represented by α-Mg, β-Li, thin-plate and faceted particles of an AlLi phase, and particles of a MgLi₂Al θ-phase. The θ-phase dissolves in the matrix in the initial stage of the solution treatment, which causes growth in the hardness of the alloy. At a temperature above 350°C the AlLi phase dissolves giving way to short rod-like precipitates of a θ-phase, which remain steady in the process of solution treatment. The hardness of the alloy deceases in this stage for this reason.