Oxidation behaviour of a Cu-Zr-Al bulk metallic glass

Cu_58.1Zr_35.9Al₆ bulk metallic glass (BMG) rod samples were prepared by suction casting into a water-cooled copper mould. The amorphous structure was confirmed with X-ray diffraction. The T_g and T_x were 760K and 799K, respectively, from differential scanning calorimetry (DSC) results. Thin disc samples were cut and oxidized at temperatures from 573K to 773K in an oxygen atmosphere inside a thermogravimetric analyzer. The oxidation kinetics can be described with a parabolic rate law from 673K to 753K but follows a linear rate law at 573K to 653K and 773K. The oxidation products are mainly Cu₂O, CuO and tetragonal ZrO₂ based on X-ray diffraction and grazing incidence XRD (GIXRD) results. However, a very thin layer of Al₂O₃, with thickness of only tens of nanometers, on the top surface of the oxide layer was revealed by Auger electron spectroscopy (AES) depth profiles. This aluminium oxide layer is thought to contribute to the exceptionally good oxidation resistance at elevated temperatures compared with that of Cu₆₀Zr₃₀Ti₁₀ we reported previously. © 2008 Advanced Study Center Co. Ltd.