Phase equilibria of the ternary Ag-Cu-Ni system and the interfacial reactions in the Ag-Cu/Ni couples

The phases formed at the interfaces of nickel and Ag-Cu alloys were determined by studying the reaction diffusion couples together with the isothermal sections of the Ag-Cu-Ni system at the annealing temperatures. Phase equilibria at 860, 795 and 700 °C, were determined by both experimental investigation and model calculation. The reaction diffusion couples were prepared with either the Ag-15 wt% Cu alloy with nickel foil, or Ag-28 wt% Cu alloy with nickel foil, and were annealed at the three above-mentioned temperatures. The interfaces of the reaction layers in the couples were non-planar. By using microscopes and EPMA, the phase sequences formed in the reaction diffusion couples were determined. These diffusion paths were in agreement with the phase equilibria study, and it demonstrated that the tie triangle shifted towards the nickel side as temperature increased. The thickness of the reacted layers was determined by using an image analyser, and a parabolic growth was found for the Ni/Ag-28 wt% Cu couple annealed at 795 °C.