Phase equilibria and solidification properties of Sn-Cu-Ni alloys

Ternary Sn-Cu-Ni alloys were prepared and annealed at 240°C. The annealed alloys were metallographically examined and the equilibrium phases formed were identified on the basis of compositional determinations and x-ray diffraction (XRD) analysis. The isothermal section of the ternary Sn-Cu-Ni system at 240°C was proposed on the basis of experimental results of this study and related information on phase equilibrium available in the literature. The binary compounds, Cu₆Sn₅, Ni₃Sn₂, and Ni₃Sn₄, have very extensive ternary solubility. Continuous solid solutions form between Cu and Ni as well as between Cu₃Sn and Ni₃Sn. In addition to the isothermal section, the liquidus projection of the Sn-Cu-Ni system was determined based on results from the existing literature. Interfacial reactions between Sn-Cu alloys and Ni substrate and the primary solidification phases of various Sn-Cu-Ni alloys were also examined in this study.