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

Cu58.1Zr35.9Al6 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.