超軽量Mg-Li-Al合金の熱処理特性および機械的性質 Heat treatment characteristics and mechanical properties of superlight Mg-Li-Al alloys
Mg–17~21 mass%Li–7.2~12.4 mass%Al ternary alloys were melted in order to improve the specific strength, and their heat treatment characteristics and tensile properties were investigated. Specific gravity of investigated alloys is in the range between 1.20 and 1.34, which is lower than that of the conventional Mg–Li alloys. The investigated alloys exhibit a marked decrease in lattice parameter and consequently are hardened by the isothermal holding at the temperature higher than 200°C, but their elongation decreases remarkably. Alloying elements are solutionized to some extent and the growth of recrystallized grains are restricted by shortening the holding time at 300°C or 350°C. Consequently, high strength and reasonable elongation can be obtained by such a heat treatment. The tensile strength of both as-rolled and as-quenched specimens increases with a decrease in lithium content and an increase in aluminum content. Additionally, age hardening at room temperature and 50°C occurs in the specimens quenched after isothermal holding at 350°C for 1 h. The appearance of side-bands in the results of X-ray diffraction patterns suggests that the hardening may be attributed to spinodal decomposition.
軽金属 47(4), 195-201, 1997-04-30
The Japan Institute of Light Metals