Effect of Ca and CaO on the High Temperature Oxidation of AZ91D Mg Alloys

Abstract

Magnesium alloys of AZ91D, AZ91D + (1, 3, 5) mass% Ca, and AZ91D + (0.5, 1) mass% CaO were cast and oxidized at high temperature in atmospheric air in order to study the effect of Ca and CaO on the oxidation. The microstructure of the CaO-added alloys was similar to that of the Ca-added alloys. Ca and CaO both formed Al₂Ca in the alloys, but Ca was more effective than CaO in increasing the oxidation resistance of Mg alloys. The microstructure and composition of the scale formed on the CaO-added alloys were similar with those on the Ca-added alloys.