The oxidation behavior of Mg-Er binary alloys at 500 ℃

Thermodynamics and kinetics of the oxidation behavior of magnesium-erbium (Mg-Er) alloys at 500 ℃ were studied. The observed protective oxidation behavior, which follows parabolic kinetics, can be attributed to the formation of compact Er2O3 surface layer and continuous dissolution and diffusion of Er from the matrix. The surface film of Mg-8.1Er (wt%) alloy was composed of four sublayers, with the double Er2O3 layers consisting of a compact fine-grain layer and an underlying coarse-columnar-grain layer providing the protective effect. A four-stage oxidation process composed of three transient reaction-controlled oxidation processes and followed by a diffusion-controlled oxides growth process is proposed.