Effect of temperature on the initial stages of oxidation of γ-Al4Cu9(110)

Abstract

Combined X-ray photoemission spectroscopy and low energy electron diffraction investigations have been performed to study the influence of temperature on the first stages of oxidation of the (110) surface of γ-Al4Cu9 complex metallic alloy in the pressure range 2–6×10−7mbar. The oxidation mechanism is driven by aluminium segregation. At 115K, a pure aluminium oxide film is formed, which does not present any long range order. CuO bonds are never observed. The lower oxidation kinetics compared to that previously observed at room temperature is due to blocking of the oxygen dissociation and/or a decrease in the aluminium segregation. However, aluminium segregation is still observed, even for this very low temperature, due to the low energy value of the activation energy for aluminium diffusion in γ-Al4Cu9 (0.65±0.12eV) which is related to the presence of two vacancies in the crystal structure. At 925K, fast aluminium segregation and possible oxygen diffusion into the bulk leads to the formation of domains or clusters of γ-like alumina either on top of or, more likely, below the surface.