Effects of alloying on oxidation of Cu-based bulk metallic glasses

The oxidation kinetics and the effects of alloying on the oxidation behaviors of copper-based bulk metallic glasses were studied. The oxidation kinetics, oxide compositions, and structures were investigated by thermogravimetric analysis (TGA), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. Both the TGA results and the XPS depth profile measurements showed that the oxidation resistance of Cu₆₀Zr₃₀Ti₁₀ bulk metallic glass was improved by adding Hf, but it deteriorated when it was alloyed with Y. The oxide phases were found to be ZrO₂, Cu₂O, and CuO in samples heated at 573 K while an additional metallic Cu phase was detected in the ones heated at 773 K. A porous oxide structure was observed in the (Cu_0.6Zr_0.3Ti_0.1)₉₈Y₂ metallic glass oxidized at 673 K, and the poor oxidation resistance of the alloy is attributed to the porous structure.