Modeling of the thermodynamic properties of melts of the ternary Sn―Zr―Co system

Abstract

Literary data on phase equilibria in alloys of binary systems Sn―Zr, Sn―Co, Zr―Co and their thermodynamic properties in the liquid state are critically analyzed. It is shown which of the available literature data is the most reliable and used in the calculations. Extrapolation of the experimental data for Sn―Zr alloys to the entire range of compositions allowed us to establish a minimum mixing enthalpy (–55 kJ / mol at x_Zr = 0,6). This correlates with the Δ_fH of compound Zr₅Sn₃, which is more exothermic (–71,2 kJ/mol). An analysis of all known thermochemical properties of Sn―Co aqlloys showed that the most reliable ones are those established in the last work. The study in this work was performed by the calorimetry method (ΔH_min =  –1,3 kJ/mol at x_Co = 0,55). This is correlated with the fact that Sn and Co form several not very refractory compounds (one that melt congruently at 1553K and two incongruently). The minimum enthalpy of mixing alloys of the Co―Zr system at 1800 K is –38 kJ/mol at x_Zr = 0,45. This correlates with the behavior of these alloys in the solid state. According to the state diagram of the Co―Zr system, its components form five intermediate phases. The enthalpy of mixing of the alloys of the Sn―Zr―Co ternary system was calculated according to the different "geometric" and "analytical" Redlich-Kister models. It is established that according to the calculations for all models, the minimum enthalpy of mixing is Zr₅Sn₃. It is found that the calculated enthalpies of the alloys mixing of the ternary Sn―Zr―Co system correlate with the state diagram.