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 fccA I (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 (Ni(3)Sn_HT, Ni(3)Sn(2)_HT, Ni(3)Sn(2)_LT, Ni(3)Sn(4)), 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. Ni(3)Sn_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. (c) 2005 Elsevier Ltd. All rights reserved.