A thermodynamic evaluation of the Ag-Sn system
Résumé
All the different solution phases and compounds of the Ag-Sn system have been analyzed in terms of thermodynamic models based on selected and agreed values for the lattice stabilities of the pure elements. A set of new self-consistent parameters has been obtained by using the well-known optimization procedure developed by Lukas et al. Calphad, 1 (1977) 225, which takes into account all the available experimental information with its accuracy concerning both thermodynamic properties and phase equilibria data. Phase diagram and characteristic thermodynamic functions have been calculated and compared to the experimental values with the THERMODATA software. A satisfactory agreement has been obtained by using nineteen optimized coefficients for more than five hundred experimental points, with a simple substitutional model for solution phases and a linear approximation for the temperature dependency of the Gibbs energy of the compound Ag3Sn ; the short range order of that phase has not been modelled in a first step. The remaining difficulties concerning the invariant reaction between the liquid phase and the two solid solution phases, fcc and hcp in the rich silver region are discussed.