Role of Al 2O 3 layer in oxidation resistance of Cu–Al dilute alloys pre-annealed in H 2 atmospheres

Abstract

Copper was alloyed with small amounts of Al (0.2, 0.5, 1.0 and 2.0 mass%) to improve the oxidation resistance. Copper (6 N) and the Cu–Al alloys were oxidized at 773–1173 K in 0.1 MPa oxygen atmosphere after hydrogen annealing at 873 K. Continuous very thin Al 2O 3 layers were formed on the surface of all Cu–Al dilute alloys during the hydrogen annealing. Oxidation resistance of Cu–Al alloys was improved especially for Cu–2.0Al at 773–973 K, while it decreases on increasing the oxidation temperature. Cu–Al alloys followed the parabolic rate law at 1173 K, but most of other cases do not at and below 1073 K. Oxidation resistance for Cu–Al alloys was found relevant to the maintenance of the thin Al 2O 3 layer at the Cu 2O/Cu–Al alloy interface.