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Abstract: Air-oxidation behavior of a Zr50Cu43Al7 bulk metallic glass (ZCA7-BMG) was studied over the temperature range of 400–500°C. The oxidation kinetics of the ZCA7-BMG generally followed a multiple-stage parabolic-rate law with its steady-state parabolic-rate constants (k p values) decreasing with increasing temperature, indicative of the occurrence of kinetics inversion. The scales formed on the ZCA7-BMG were strongly dependent on temperature, consisting mostly of tetragonal ZrO2 and CuO, and minor amounts of monoclinic ZrO2 and Cu2O at 400°C, while Cu2O was completely absent at T ⩾450°C. In addition, a minor amount of Al2O3 was further observed after the oxidation at 500°C, whose formation is responsible for the lowest oxidation rate, as compared to those at T ⩽450°C. [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]