Oxidation behavior of AgCuTi brazing alloys

Two kinds of brazing alloys, Ag56.9Cu37.6Ti5.5 and Ag54.7Cu36.3Ti9.0, were brazed on Si3N4 substrate and their oxidation behavior was investigated at 400, 500 and 600°C in air. Under the experimental conditions, Ag was not oxidized, whereas Cu and Ti were oxidized parabolically. The oxide scale formed on the brazing alloy consisted of a mixture of Cu2O and CuO, which grew by the outward diffusion of cations. Beneath this external scale, an Ag-enriched zone was formed due to the selective oxidation of Cu at the surface. Some isolated and small Ag particles were present at the oxide-gas interface. Also, the inward diffusion of oxygen led to the formation of internal oxides of TiO2 and Ti2O3.