The solution and room temperature aging behavior of Mg-9Li-xAl(x = 3, 6) alloys

As-cast Mg-9Li-3Al(LA93) and Mg-9Li-6Al(LA96) alloys were prepared under the ambient of pure argon, and the effect of solution treatment and room temperature (RT) aging on the microstructure and microhardness of the alloys were investigated. The results show that the main phase compositions of the two alloys both consist of α(Mg), β(Li), AlLi phase, besides that there is θ(MgLi2Al) phase in LA96. After solid solution treatment, AlLi phase can completely be dissolved into the matrix, while θ phase is not fully dissolved into the matrix. In LA93 and LA96 alloys, AlLi phase precipitates from matrix during the 24 h RT aging. When the aging time increases to 48 h, more AlLi phase turns up and appears to aggregate which results in the decrease of hardness, and the transformation of θ phase into the equilibrium phase (AlLi) in LA96 also causes the hardness decrease.