The oxidation behavior of an Fe61B15Zr8Mo7Co5Y2Cr2 bulk metallic glass at 650 °C in various oxygen-containing environments

The oxidation behavior of an Fe61B15Zr8Mo7Co5Y2Cr2 bulk metallic glass (Fe7-BMG) was investigated in three oxygen-containing atmospheres over the oxygen partial pressure range of 10(3)-10(5) Pa at 650 degrees C. The oxidation kinetics of the Fe7-BMG followed the parabolic rate law in all cases, indicating that solid-state diffusion is the rate-controlling step during oxidation. The oxidation rate constants (k(p) values) increased with increasing oxygen partial pressure, implying a typical scaling behavior with a p-type semi-conductivity. Duplex scales formed on the Fe7-BMG consisted of an outer layer of mostly iron oxides (Fe2O3/Fe3O4) and minor amounts of B2O3, and a heterophasic inner layer of mostly tetragonal-ZrO2 (t-ZrO2) intermixed with non-oxidized intermetallic phases. (C) 2008 Published by Elsevier Ltd.