Oxidation Resistance Failure Of Dilute Cual Alloys At 800 Degrees C

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 degrees C and compared with the case at 400 degrees C. The OR of dilute CuAl alloys at 800 degrees C can be distinctly improved at the initial oxidation stage as well as 400 degrees C. However, at 800 degrees C, the OR gradually declines as the oxidation progresses, which considerably differs from the observation at 400 degrees C with the stable OR. The results show that the decline of the OR at 800 degrees 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.