Microstructure and mechanical properties of Mg–Zn–Y–Mn magnesium alloys with different Zn/Y atomic ratio

The effects of Zn/Y atomic ratio on the microstructure and mechanical properties of Mg–Zn–Y–Mn alloys were studied and analyzed using optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD), differential scanning calorimetry (DSC), microhardness testing, high-temperature creep testing and an electronic universal testing machine. The results indicated that when Zn/Y ratio is 3:1, the alloy is mainly composed of α-Mg, I phase and W phase; when Zn/Y ratio is 1.5:1, the alloy is mainly composed of α-Mg and W phase; the alloys are all composed of α-Mg, W phase and LPSO phase when the Zn/Y ratio decreases to 1:1 or 0.8:1. With the decrease of Zn/Y ratio, the yield strength and tensile strength of alloy first increase and then decrease; the high-temperature creep resistance increases first and then decreases, and the elongation shows the trend of decreasing, increasing and then decreasing again. In total, the Mg94Zn2.5Y2.5Mn1 alloy exhibits the best mechanical properties and the best creep resistance, which is mainly related to the type and amount of the second phase.