Thermodynamic optimization of the Ni–Sn binary system

Through the CALPHAD method and based on experimental data of thermodynamic properties and phase boundaries, the phase diagram of the Ni–Sn binary system has been reassessed. The liquid and fcc_A1 (terminal rich nickel solid solution) phases were described by using a simple substitutional model, the excess Gibbs energy being formulated with a Redlich–Kister expression. The other intermediate phases (Ni3Sn_HT, Ni3Sn2_HT, Ni3Sn2_LT, Ni3Sn4), were described with a several sublattice model with different formula; the Gibbs energy of the reference compounds was assumed to be linear, and the binary interaction terms on the sub-lattices to be constant. Ni3Sn_LT was treated as a stoichiometric compound. The solubility of Ni in the terminal phase bct_A5(Sn) was neglected because it is very small. Finally a set of self-consistent thermodynamic parameters for all condensed phases in the Ni–Sn binary system was obtained, which can reproduce most of the experimental data.