Air oxidation of an Fe 72B 22Y 6 bulk amorphous alloy at 600–700 °C

Abstract

The oxidation behavior of the Fe 72B 22Y 6 bulk metallic glass and its crystalline counterpart was studied over the temperature range of 600–700 °C in dry air. The results showed that the oxidation kinetics of both glassy and crystalline alloys in general follow a parabolic rate law although a two-stage kinetics was noted at 700 °C for the glassy alloy. The oxidation rates of the two alloys increased with increasing temperature, and the parabolic rate constants of the glassy alloy are much lower than those of the crystalline counterpart. The scales formed on the glassy alloy consisted mainly of boron oxide (B 2O 3) and minor amounts of iron oxides (Fe 3O 4/FeO). Conversely, duplex scales formed on the crystalline counterpart were composed of an outer layer of Fe 2O 3 and an inner layer of Fe 3O 4–YBO 3 mixture. The formation of B 2O 3 is responsible for the reduced oxidation rates of the glassy alloy as compared to those of crystalline counterpart.