High temperature oxidation of AZ31 + 0.3 wt.%Ca and AZ31 + 0.3 wt.%CaO magnesium alloys

Magnesium alloys of AZ31 + 0.3 wt.%Ca and AZ31 + 0.3 wt.%CaO were cast and oxidized between 450 and 650 °C in atmospheric air. The initially added Ca and CaO enabled to cast the alloys in air without using environmentally hazardous SF6 gas, by forming a thin CaO-rich barrier layer at the surface during casting. A thin CaO-rich barrier layer was also formed at the surface during oxidation in air, thereby increasing the oxidation resistance of the AZ31 alloy considerably. The initially added Ca and CaO reacted with Al to become Al2Ca along the grain boundaries of the AZ31 alloy during casting.

► AZ31 + 0.3 wt.%CaO alloys were cast and oxidized between 450 and 650 °C in air.
► Initially added CaO particles increased the oxidation resistance of Mg alloys.
► Oxidation-resistant, environment-friendly CaO-added Mg alloys were developed.