Effect of Ca and Y additions on oxidation behavior of magnesium alloys at high temperatures

Oxidation and ignition of magnesium alloys at elevated temperature were successfully retarded by additions of Y and Ca, which could be melted at 1173 K in air without any protection. Thermogravimetric measurements in dry air revealed that the oxidation dynamics curves of Mg-2.5Ca alloy and Mg-3.5Y-0.79Ca alloy at high temperatures followed the parabolic-line law or the cubic-line law. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the oxide film on the surface of Mg-3.5Y-0.79Ca and Mg-2.5Ca alloys exhibited a duplex structure, which agreed with the results of thermodynamic analysis. By comparison, the ignition-proof effect of the combination addition of Y and Ca was better than that of the single addition of Ca.