Thermodynamic properties of melts of Cu—Yb and Cu—In—Yb systems

Abstract

The partial and integral enthalpies of mixing of the melts the Cu-Yb system in the composition range 0 < xCu <0,7 and for 5 sections of Cu – In – Yb system with a constant ratio of the other two components (xCu/xIn=0,36/0,64; xCu/xIn= 0,62/0,38; xIn/xYb= 0,62/0,38; xCu/xYb =0,64/0,36; xCu/xYb =0,21/0,79) to x3 = 0.3 by method isoperibolical calorimetry in the temperature range 1453-1473K first were determined. Using the model of ideal associated solutions (IAR), all the thermodynamic properties (Gibbs energies of mixing melts, enthalpy and entropy of formation of intermetallic compounds and associates) of the Cu–Yb system were calculated. It turned out that the activity of the components in the melts of this system exhibit small negative deviations from ideal solutions. Calculations using the IAR model also made it possible to establish that with increasing temperature it increases slightly, but more significantly. Also were obtained the coordinates of the liquidus curve of the diagram state of the studied system. The principal contribution to the enthalpies of mixing in the liquid alloysof the Cu–In–Yb system gives the border subsystem In–Yb. Because the minimum of the mixing enthalpies in the ternary sysytem Cu–In–Yb shifts towards the equiatomic alloy concentration of subsystem In–Yb (-36,5±1,0) at Т= 1453 К. Using the experimental partial and integral enthalpies of mixing, the activities of the components in the melts of binary limiteyted system of melts of the Cu–In–Yb ternary system, calculated according to «geometric» and the Redlich-Kister-Mujian models in a wide range of concentrations. It is established that the experimental ∆H, and calculated analogical datas according to the Redlich-Kister-Mujianu model agree between. It is shown that the activities of the components in the melts of this system, calculated according to the Redlich-Kister model, show small negative deviations from ideal solutions at 1453 K. From these of data calculated G, S. It was found that Gmin = –19 kJ/mol, Smin = –15 J/mol*K for the alloy In0,5Yb0,5. This correlates with the determined thermochemical properties of the melts Cu –In– Yb system. Keywords: calorimetry, the melts, intermetallic, thermodynamic properties, Cu, Yb, In, the model of ideal associated solutions, the Redlich—Kister—Mujianu model, phase equilibria.