Effects of Si addition on the oxidation behavior of a Cu–Zr-based bulk metallic alloy

The effect of Si addition on the oxidation of (Cu43Zr43Al7Ag7)99.5Si0.5 bulk metallic glass (CZ43S-BMG) was investigated over the temperature range of 375–500 °C in dry air. The results generally showed that the oxidation rates of the CZ43S-BMG followed a multi-stage parabolic-rate law, and the oxidation rate constants (kp values) fluctuated with increasing temperature. It was found that the kp values of the CZ43S-BMG were slightly slower than those of the Si-free glassy alloy (Cu43Zr43Al7Ag7, named as CZ43-BMG). The scales formed on the CZ43S-BMG strongly depend on temperature, consisting of 3 different modifications of ZrO2 and CuO, and minor amounts of Cu2O (formed at T ≥ 425 °C) and Al2O3 (only detected at 500 °C). In addition, the glassy substrate remained amorphous nature at T ≤ 400 °C, while it transferred to the crystalline phases of Cu10Zr7, ZrAl, and ZrSi2 after the oxidation at higher temperatures.