Air-oxidation of a Zr50Cu43Al7 bulk metallic glass at 400–500 °C

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 (kp 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.