Role of heat treatment temperatures on mechanical properties and corrosion resistance properties of Mg-10.16Li-8.14Al-1.46Er alloy

The microstructure and phase evolution of Mg-10.16Li-8.14Al-1.46Er alloy of as-cast, 250 ℃+12 h, 300 ℃+12 h, and 400 ℃+12 h were studied by optical microscopy, scanning electron microscope, and X-ray diffraction. The mechanical properties of Mg-10.16Li-8.14Al-1.46Er alloy in different states were tested by microhardness tester and tension tester. The corrosion resistance of Mg-10.16Li-8.14Al-1.46Er alloy in different states was measured by electrochemical workstation combined with hydrogen evolution and mass loss tests. The results show that the microstructure of as-cast Mg-10.16Li-8.14Al-1.46Er alloy consists of α, β, AlLi, Al3Er and MgAlLi2 phases. Changes of microstructure are morphology and quantity of α phase, and second phases of MgAlLi2 and AlLi by heat treatments at different temperatures. The best comprehensive tensile properties of Mg-10.16Li-8.14Al-1.46Er at 400 ℃ are attributed to the α phase structure, solution strengthening and second phase strengthening. After heat treatments at different temperatures, the corrosion resistance of Mg-10.16Li-8.14Al-1.46Er was improved compared with as-cast samples. The Mg-10.16Li-8.14Al-1.46Er alloy has the best corrosion resistance at 250 ℃ due to the best homogenization at this temperature.