Effect of Gas Pressure on the Oxidation Behavior of Cu and Cu Alloys

This study investigated the effect of gas pressure and alloying elements on the oxidation behavior of copper. Copper alloys containing 1 wt.% of zinc, nickel, or manganese were cast using vacuum induction melting, followed by solution treatment at 400°C for 60 minutes. Oxidation were conducted at 700°C for 60 minutes under pressures of 101325, 20, and 10 Pa. The oxide layers formed at atmospheric pressure on both the pure copper and copper alloys naturally delaminated. In contrast, the oxide layers formed under low-pressure conditions remained intact without delamination. This improved bonding strength between the copper matrix and Cu2O was attributed to the formation of large grains and dense oxide layer, which increased the contact area with the copper substrate. Additionally, the oxide layers formed under low-pressure exhibited higher dislocation density, which reduced lattice mismatch and interface energy, thereby contributing to the formation of stable interface. In copper alloys, thicker oxide layers were observed compared to pure copper, with voids detected between the oxide layer and the copper substrate. These voids were presumed to be Kirkendall voids, resulting from the difference in diffusion rates between copper and the alloying elements. However, adhesion evaluations indicated that these voids did not significantly impact interfacial adhesion. Through interface control, dense and stable oxide layers were successfully formed on both pure copper and copper alloys.