Effect of heat treatment on microstructure and properties of Mg-12Y-1Al alloy

The microstructure of Mg-12Y-1Al alloy with solution treatment and aging treatment was studied by optical microscope, X-ray diffraction and scanning electron microscope. The mechanical properties of the alloy before and after heat treatment at room temperature and 200 ℃ were analyzed by tensile test, and the corrosion resistance of the alloy before and after heat treatment was tested by electrochemical methods. The results show that the as-cast microstructure of Mg-12Y-1Al alloy is composed of α-Mg matrix, Mg24Y5 phase and Al2Y phase. Mg-12Y-1Al alloy has excellent high-temperature thermal stability. After solution treatment at 520 ℃ for 16 h(T4), the grain size does not increase, and new long period stacking ordered(LPSO) phase forms; the subsequent aging treatment at 225 ℃ for 30 h(T6) has little effect on the microstructure. Compared with the properties at room temperature, the ultimate tensile strength of T4 alloy at 200 ℃ does not decrease, but the elongation increases from 1.3% to 12.5%. Moreover, the corrosion resistance of Mg-12Y-1Al alloy is improved after solution and aging treatment, and the corrosion current density decreases from 2.799×10-5 A/cm2 to 1.551×10-5 A/cm2.