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 degrees C in air. Under the experimental conditions, Ag wa s not oxidized, whereas Cu and Ti were oxidized parabolically. The oxide sc ale formed on the brazing alloy consisted of a mixture of Cu2O and CuO, whi ch grew by the outward diffusion of cations. Beneath this external scale, a n Ag-enriched zone was formed due to the selective oxidation of Cu at the s urface. Some isolated and small Ag particles were present at the oxide-gas interface. Also, the inward diffusion of oxygen led to the formation of int ernal oxides of TiO2 and Ti2O3. (C) 1999 Elsevier Science S.A. All rights r eserved.