Phase equilibria of the Ag–Sn–Cu ternary system

Phase equilibria of the Ag–Sn–Cu ternary system have been determined experimentally as well as using the calculation of phase diagram (CALPHAD) method. Various Ag–Sn–Cu alloys were prepared to study the isothermal sections of the Ag–Sn–Cu ternary system at 240 and 450 °C. No ternary compounds were found and all the binary compounds had only limited ternary solubility. The ∈₁–Cu₃Sn phase is a very stable phase. It is in equilibrium with the Ag, ζ–Ag₄Sn, ∈₂–Ag₃Sn, η–Cu₆Sn₅, and Cu phases at 240 °C, and is in equilibrium with the Ag, ζ, ∈₂, L, and δ–Cu₄Sn phases at 450 °C. Thermodynamic models of the Ag–Sn–Cu ternary system were developed based on available thermodynamic models of the constituent binary systems without introducing ternary interaction parameters. The isothermal sections at 240 and 450 °C were calculated, and the results were in good agreement with those determined experimentally. In addition to the isothermal sections, stability diagrams of Sn and Cu were calculated as well.