Oxidation behavior of Cu-38at%Zn foils after surface mechanical attrition treatment

A commercial Cu-38at%Zn foil was subjected to surface mechanical attrition treatment (SMAT) processing. The isothermal oxidation behavior of the SMAT Cu-38at%Zn over the temperature range of 773 ∼ 1,123 K was studied and compared with that of original Cu-38at%Zn. Characterization of the oxidized specimens was conducted using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Results show that the oxidation rates of the SMAT specimens are significantly higher than those of the original specimens. The activation energies during oxidation were calculated to be 136 kJ mol -1 for the SMAT Cu-38at%Zn and 176 kJ mol -1 for the original Cu-38at%Zn, based on the parabolic growth constant analyses. The intermediate layer between the oxide scale and substrate includes white a-Cu(Zn)/zinc oxide (ZnO), a solid solution with Cu as solvent and Zn as solute, narrow zone and dark internal ZnO oxide zone for the original specimens, and only a-Cu(Zn)/ZnO narrow zone for the SMAT specimens. The oxidation kinetics for the two types of specimens is explained by the difference of ion diffusion and defect in the oxide scales.