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Abstract: The oxidation behavior of a commercial Co69B12Si12Fe4Mo2Ni1 amorphous ribbon (Co6-AR) was studied over the temperature range of 400–600°C in dry air. The results showed that virtually no oxidation occurred at 400°C. On the other hand, the oxidation kinetics of the Co6-AR alloy at 450–600°C generally followed a multi-stage parabolic-rate law, and the parabolic-rate constants (k p values) tend to increase with increasing temperature. It was found that the oxidation rates of the glassy alloy are slower than those of pure Co, indicative of a better oxidation resistance. An exclusive scale of CoO was observed after the oxidation of the glassy alloy in the temperature range of interest, and several crystalline phases formed on the substrate beneath the scale, consisting of pure Co (both FCC and HCP structures), Co3B, Co2Si, CoFe, and Co2B (absent at 450°C), which indicated the occurrence of crystallization. [Copyright &y& Elsevier]

Abstract: 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 (k p values) fluctuated with increasing temperature. It was found that the k p 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. [ABSTRACT FROM AUTHOR]