Air-Oxidation Behavior of a Cu 60 Hf 25 Ti 15 Bulk Metallic Glass at 375–520 °C

The oxidation behavior of a Cu 60 Hf 25 Ti 15 bulk metallic glass was studied over the temperature range of 375–520 °C in dry air. The oxidation kinetics of the amorphous alloy generally followed the parabolic law at all temperatures, with an oxidation rate increasing with temperature. The oxidation rates of the amorphous alloy were much higher than those of polycrystalline pure-Cu, implying that the additions of Hf and Ti accelerated the oxidation reaction. The composition of the scales formed on the amorphous alloy was strongly temperature-dependent, since they consisted mostly of Cu 4 O 3 and CuO with minor amounts of HfO 2 at T ≤ 450 °C, while mostly CuO with minor amounts of HfO 2 and Cu 2 TiO 3 were detected at higher temperatures. In addition, nanocrystalline Cu 51 Hf 14 and Cu 3 Ti 2 phases were detected on the substrate after oxidation at T ≥ 450 °C, indicating the occurrence of phase transformation.