Abstract:The oxidation behaviour of molten ZK60 and ME20 magnesium alloys in 1% 1,1,1,2-tetrafluoroethane/air atmospheres at 720 °C was compared with that of molten magnesium. The oxidation kinetics of these three melts was determined by thermograyimetric measuring instrument, and the surface films of the oxidized samples were examined by scanning electron microscope (SEM), X-ray diffractometry905hineseming; strain rates as: temperature (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that the oxidation rate of molten ZK60 or ME20 alloys is much lower than that of molten magnesium in 1% 1,1,1,2-tetrafluoroethane/air atmospheres. The surface film formed on the molten magnesium is composed of MgF₂, MgO and C, while the film formed on ZK60 melt mainly consists of MgF₂, MgO, C and some ZrF₄, and the film on ME20 mainly consists of MgF₂, MgO, C and a small amount of CeF₄. The good oxidation resistances of ZK60 and ME20 alloy melts may be caused by their major alloying elements Zr and Ce, respectively.

Key words: ZK60 alloy; ME20 alloy; magnesium alloy melt; Mg melt; 1,1,1,2-tetrafluoroethane; alloying element; oxidation