Characteristic Depth Profiles of Surface Layers Formed in Cu-based Alloys by Annealing in Low Partial Pressure of Oxygen

Secondary ion mass spectrometry (SIMS) has been used for characterizing the depth distribution of alloying elements in three different copper-based dilute alloys, i.e. copper-chromium, copper-iron and copper-nickel-silicon alloys, which were annealed at high temperatures under low oxygen partial pressure. SIMS depth profiles showed that oxygen penetrated into the copper-based alloys, and chromium and silicon were enriched to the surface side so as to form oxides during annealing. Chromium and silicon were depleted beneath the enriched layer. On the other hand, depth profiles of iron and nickel were similar to that of copper. These phenomena were likely to be associated with the reactivity of alloying elements with oxygen. The formation kinetics of the depleted zones of chromium and silicon was discussed coupled with the selective oxidation of these alloying elements.