Thermodynamic assessment of the Bi–K binary system

Highlights: ► For the liquid phase, the associate model was used with the constituent species Bi, BiK, BiK3 and K. ► A self-consistent set of thermodynamic parameters was obtained. ► The experimental information were well reproduced by the optimized thermodynamic data. - Abstract: The thermodynamic assessment of the Bi–K system was carried out by using the Calculation of Phase Diagrams (CALPHAD) method on the basis of experimental thermodynamic data and phase equilibrium measurements. To describe the short-range ordering behavior of the liquid phase, the associate model was used with the constituent species Bi, BiK, BiK3 and K. All the intermetallic compounds with no experimentally determined solubility ranges were treated as stoichiometric compounds. The solution phases, the Bi-rich terminal phase RhombohedralA7 and the K-rich terminal phase BCCA2, were treated as the pure substances since the solubility of the second alloying element is extremely small in each of these phases. A set of self-consistent thermodynamic parameters was obtained for the Bi–K system and the CALPHAD results can reproduce the experimental thermochemical properties and the measured phase equilibrium relations well.