Oxidation Resistance Failure of Dilute CuAl alloys at 800 °C

Abstract

Oxidation is a major failure mode for the application of Cu in industry. To address this issue, alloying Cu with Al presents a potential solution due to the Al2O3-rich thin film formed during a pre-annealing process. The low oxidation resistance (OR) of dilute CuAl alloys that are oxidized at high temperatures is a critical issue due to their long-term exposure to an aerobic environment. Thus, the ORs of dilute CuAl alloys with 0.2–2.0 wt.% Al pre-annealed in a hydrogen atmosphere were examined at 800 °C and compared with the case at 400 °C. The OR of dilute CuAl alloys at 800 °C can be distinctly improved at the initial oxidation stage as well as 400 °C. However, at 800 °C, the OR gradually declines as the oxidation progresses, which considerably differs from the observation at 400 °C with the stable OR. The results show that the decline of the OR at 800 °C starts from the oxide button formation at the surface, and the growth and coarsening of these buttons cause nonuniform oxide scale formation. As the oxidation proceeds, the remnant Al2O3-rich thin film does not move with the Cu2O/CuAl interface, which is induced by the impeded outward diffusion of Cu atoms. The slowed diffusion of Cu atoms originates from the remnant Al2O3-rich thin film and the Al2O3 particles that are newly formed in the CuAl alloys due to the internal oxidation of Al.