Thermodynamic optimization of the In-Pb-Sn system based on new evaluations of the binary borders In-Pb and In-Sn

A new assessment of two binary In-Pb and In-Sn systems and a thermodynamic description of the ternary In-Pb-Sn system are presented in this paper. The modeling of each system is carried out in the same way, by taking into consideration available thermodynamic and phase diagram data. The thermodynamic description of pure elements is taken from the Scientific Group Thermodata Europe (SGTE) data bank [Calphad 15 (1991) 317]. The lattice stability of In, Pb and Sn in the γ-phase, which is not available, is evaluated. The liquid phase, the three primary solid solutions (In), (Pb) and (βSn), and the two intermediate phases β and γ, are described by Redlich-Kister-Muggianu formalism as disordered solutions. The thermodynamic description is performed according to the Calphad method [Computer Calculation of Phase Diagrams, Academic Press, New York (1970)] by using the Thermo-Calc software [Calphad 9 (1985) 153] and the Parrot program [Ph. D. Thesis, Royal Institute of Technology, Stockholm (1984)]. The adjustable parameters obtained and the calculated phase diagrams are presented. For the two binary systems and the ternary system, some calculated thermodynamic functions are compared with experimental values of liquid alloys as well as of solid alloys.