Air-oxidation of a Cu50Zr50 binary amorphous ribbon at 350-425 °C

The oxidation behavior of a binary Cu50Zr50 bulk amorphous ribbon (CZ2-AR) was studied over the temperature range of 350-425 °C in dry air. The oxidation kinetics of the CZ2-AR generally followed a parabolic-rate law, indicating that diffusion is the rate-controlling step during oxidation. The oxidation rates of the CZ2-AR were strongly temperature-dependent, with its scaling-rate constants (ks values) increasing with temperature. Duplex scales formed on the CZ2-AR alloy were composed of an outer-layer of exclusive CuO and of a heterophasic inner-layer of CuO, monoclinic-ZrO2 (m-ZrO2) and tetragonal-ZrO2 (t-ZrO2). In addition, the CZ2-AR substrate started to form the crystalline Cu10Zr7 phase beneath the scales during the oxidation at T ≥ 375 °C, indicative of the occurrence of the crystallization of the amorphous substrate.