The oxidation behavior of an Fe61B15Zr8Mo7Co5Y2Cr2 bulk metallic glass at 550–700 °C

Abstract The oxidation behavior of an Fe 61 B 15 Zr 8 Mo 7 Co 5 Y 2 Cr 2 bulk metallic glass (Fe7-BMG) and its crystalline counterpart (XFe7) was studied over the temperature range of 550–700 °C in dry air. In general, the results showed that the oxidation kinetics of the Fe7-BMG and XFe7 alloys followed a parabolic-rate law, with their oxidation rates increasing with temperature. It was found that the oxidation rate constants ( k p values) of the Fe7-BMG are slightly higher than those of XFe7, indicating that the amorphous alloy underwent a fast oxidation reaction. The scale formed on the Fe7-BMG at 550 °C for 48 h was thin and heterophasic mixture of iron oxides (Fe 2 O 3 /Fe 3 O 4 ) and tetragonal-ZrO 2 (t-ZrO 2 ). At higher temperatures ( T  ≥ 600 °C), duplex scales formed on the glassy alloy consisted of an outer layer of iron oxides (Fe 2 O 3 /Fe 3 O 4 ) and minor amounts of B 2 O 3 , and of a heterophasic inner layer of mostly t-ZrO 2 intermixed with non-oxidized Fe 3 B, FeCo, and ZrB 12 . The formation of the crystalline intermetallics indicated the occurrence of the substrate crystallization at the temperature range of interest.