Oxidation Behavior of CuZr-Based Glassy Alloys at 400 °C to 500 °C in Dry Air

Abstract

The oxidation behavior of the Cu47.5Zr47.5Al5 (Cu3) and Cu47Ti34Zr11Ni8 (Cu4) bulk metallic glasses (BMGs) was studied over the temperature range of 400 °C to 500 °C in dry air. The oxidation kinetics of both alloys generally followed a multistage parabolic-rate law, and the steady-state parabolic-rate constants (k p values) fluctuated with temperature for the Cu3 BMG, but increased with increasing temperature for the Cu4 BMG. The scales formed on the BMGs were strongly dependent on the temperature and alloy composition, and were composed primarily of tetragonal-ZrO2 (t-ZrO2) and minor amounts of Al2O3, Cu2O, and CuO at 400 °C for the Cu3 BMG, while the monoclinic-ZrO2 (m-ZrO2) phase is present at T ≥ 425 °C, and the Cu2O phase is absent at 500 °C. Conversely, the scales formed on the Cu4 BMG consisted exclusively of CuO at 400 °C, while minor amounts of t-ZrO2, TiO2, and ZrTiO4 formed at 425 °C to 450 °C, and TiO was also detected at higher temperatures. It was found that both amorphous Cu3 and Cu4 substrates transformed into different crystalline phases, and were strongly dependent on temperature and duration of time.