The oxidation behavior of Cu–Zr–Ti–base bulk metallic glasses in air at 350–500 °C

The oxidation behavior of two Cu-base bulk metallic glasses (BMGs), having compositions Cu–30Zr–10Ti and Cu–20Zr–10Ti–10Hf (in at.%), was studied over the temperature range of 350–500 °C in dry air. In general, the oxidation kinetics of both BMGs followed the parabolic rate law, with the oxidation rates increasing with increasing temperature. The addition of Hf slightly reduced the oxidation rates at 350–400 °C, while the opposite results observed at higher temperatures. It was found that the oxidation rates of both BMGs were significantly higher than those of polycrystalline pure-Cu. The scales formed on both BMG alloys were strongly composition dependent, consisting of mostly CuO/Cu₂O and minor amounts of cubic-ZrO₂ and ZrTiO₄ for the ternary BMG, and of CuO, cubic-ZrO₂, and Zr₅Ti₇O₂₄ for the quaternary BMG. The formation of ternary oxides (ZrTiO₄ and Zr₅Ti₇O₂₄) was inferred to be responsible for the fast oxidation rates of the BMGs.