MICROSTRUCTURAL CHARACTERIZATION OF INTERNAL OXIDATION OF AGCU ALLOY

The internal oxidation of AgCu alloys with atomic percentage 0.8, 3.3, 6.3 and 9.5 of Cu in air at 750 degrees C and 850 degrees C has been studied. It was found that CuO particles precipitated homogeneously on the surface ai AgCu alloys except for Ag-9.5% (atomic percentage) Cu. The latter exhibited the agglomerated precipitation of CuO particle c luster on the surface. The experimental results also revealed that the nucleation and growth of CuO oxide evidently varied with the change o f Cu contents or oxidation temperature. When both Cu content and expos ure temperature were low, the precipitation and the growth of internal CuO oxide were consistent with the prediction by the classical Bohm-K ahlweit mode, but the abnormal phenomenon of nucleation and growth of the CuO oxide was observed when the Cu content or the exposure tempera ture was increased. As a result of investigation of the atomic structu re of different internally oxidized AgCu alloys, it is proposed that t he stacking fault tetrahedra(SFT), which were found in the oxidized al loys, promoted the nucleation of CuO internal oxide.