Thermodynamic Assessment of the Bi–Ni and Bi–Ni–X (X = Ag, Cu) Systems

The Bi–Ni system was reassessed by means of the calculation of phase diagrams (CALPHAD) method by considering the latest published experimental data. To maintain the compatibility in higher-order systems, the excess Gibbs energy of the solution phases was modeled with the Redlich–Kister polynomials, and a three-sublattice model, (Bi)0.3334(Ni,Va)0.3333(Va,Ni)0.3333, was used to describe the intermetallic compound BiNi with NiAs-type crystal structure. Compared with the previous thermodynamic description for the Bi–Ni system, noticeable improvements are achieved in the present work. The current thermodynamic parameters can well reproduce the newly published experimental data on thermodynamic properties. Based on the newly obtained parameters for the Bi–Ni system, as well as the thermodynamic descriptions for the Bi-Ag, Ni-Ag, Bi-Cu, and Ni-Cu systems in literature, a thermodynamic database of the Bi–Ni–Ag and Bi–Ni–Cu ternary systems was established by considering the available experimental data. The calculated phase equilibria in these ternary systems are in satisfactory agreement with experimental observations.