The effect of calcium addition to magnesium on the microstructure and compositional changes of oxide film formed at high temperature

Microstructural and compositional changes of oxide films were investigated in pure magnesium and Mg-1.51 mass%Ca alloy oxidized at high temperature. The oxide films of pure magnesium formed at high temperature above 500 degreesC were porous, whereas those of Ca-containing alloy were compact, thin and dense. II was found that the oxide films of Ca-containing alloy were basically in the amorphous state containing a high Volume fraction of CaO, while those of liquid oxidation were identified as a mixture of amorphous and microcrystalline structure. The retardation and suppression of solid and liquid oxidation at high temperature in Ca-containing magnesium alloy was caused by the formation of compact amorphous oxide films.