Effect of Mg on the Oxide Growth of Al–Cu Alloys at Elevated Temperature

Abstract

In this study, we investigated the effect of Mg on oxide growth of Al-Cu alloys at elevated temperatures. Results show that Al2Cu as eutectic phase was distributed in the as-cast microstructure of Mg-free Al-5 mass%Cu alloy, whereas Al2CuMg_S phase was formed by eutectic reactions with the addition of Mg. Scanning electron microscopy and thermodynamic calculations revealed that after oxidation at 500 °C for 30 h, Al-5 mass%Cu alloy had only slightly oxidized surfaces, whereas significantly grown oxide clusters formed as the Mg content increased. MgO and spinel were the main oxides in the Mg-containing alloys, whereas no Cu-based oxide was involved in the oxidation of the alloys. Only Al2CuMg_S phase contributed to the oxidation of the base metal and the formation of Mg-based oxides. The Al-5 mass%Cu alloy showed no inter-products with Mg-based oxides, including MgO and spinel.