XPS study of the initial oxidation of the bulk metallic glass Zr46.75Ti8.25Cu7.5Ni10Be27.5

The surface oxidation behaviour of the bulk metallic glass Zr46.75Ti8.25Cu7.5Ni10Be27.5 was investigated in situ by using X-ray photoelectron spectroscopy (XPS). The initial stages of oxidation at room temperature were studied by exposing the clean alloy specimen surface to varying doses of pure oxygen (up to 1,000 L) in an UHV chamber. Progressive oxidation of Zr, Be and Ti was observed with increasing doses, the major species in the oxide layer being Zr(IV) and Be(II) possibly existing as ZrO2, BeO, while Cu and Ni remained in their elemental forms. High temperature in situ oxidation in the temperature range 423–653 K for a fixed oxygen dose of 300 L was also investigated. Oxidation of Be was observed at all temperatures, while a sharp decrease in the oxidation of Zr and Ti was observed for temperatures at 573 K and above. The results show a preferential oxidation of Be and Zr at room temperature, while at higher temperatures oxidation is controlled by the reduction of oxides of Zr and Ti and the diffusion of oxygen into the alloy bulk. The role of the dissolved carbon impurity in the reduction of the oxides is discussed.