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.