The thermochemical properties of melts of the Al—Ce system at temperatures of (1380—1490)  3 K in range of compositions 0 < xAl < 0,38 were determined by the method of isoperibolic calorimetry. It was established that the minimum value of the enthalpy of mixing of these melts is −40,9  4.1 kJ/mol and corresponds to the melt with xAl = 0,67, and =−83,3 ± 4,8; = −200 ± 26,0 kJ/mol. Using our own and literature thermochemical data for melts and intermediate phases of the Al—Ce system, as well as its diagram state according to the ideal associated solution (IAS) model, all thermodynamic properties of melts and associates in melts and intermetallics were calculated and optimized. It was established that the calculated activities of the components in the melts of this system show large negative deviations from ideal solutions. which correlates with their thermochemical properties. The maximum mole fraction of associates CeAl2, CeAl reaches values of 0,4 and 0,24, and the other three (Ce2Al, CeAl3, CeAl5) — 0,16; 0,08, and 0,11, respectively. The minimum values of Gibbs energies and entropies of melt formation are equal to -28,2 kJ/mol and -7,6 J/mol∙K. The temperature-concentration dependences of Gibbs energies, enthalpies and entropies of melt formation and temperature for intermetallics were also calculated using the IAS model, and from them, the liquidus curve of the phase diagram of this system. As a result, complete information on the thermodynamic properties of all phases and the liquidus curve of the phase diagram of the Al—Ce system was obtained. In order to confirm the reliability of the obtained data and search for general regularities of the thermodynamic characteristics of alloying of the Al—Ce system, it was considered as a member of the series of Al—Ln(Ln-lanthanide) systems. For this, the enthalpies of formation were analyzed. intermetallics LnAl2, as well as the minimum values of thermochemical properties of melts, relative differences in molar radii and differences in electronegativities of the components of the Al—Ln systems and their dependence on the lanthanide serial number. It is shown that all dependences, except for the electronegativity differences of the components, are compatible with each other. This indicates that the thermodynamic properties of compounds and melts of Al—Ln systems are determined by the size factor. Keywords:: method calorimetry, mixing enthalpy, activity, aluminum, cerium, melts, intermetallics, thermodynamic properties, ideal associated solution model.

Enthalpies of mixing of liquid alloys are determined via isoperibol calorimetry for the Gd–Sn system throughout the range of concentrations at 1873, 1640, and 1510 K, and for the Gd–Sn–Ni system along the radial section with a constant ratio of atomic fractions of tin and nickel: xSn/xNi = 0.68/0.32 at 1873 ± 5 K up to xGd ∼ 0.25. It is found that the melts of the Gd–Sn system form with the release of a large amount of heat ( $$\Delta {{{H}}_{{\min }}}$$ = −68.4 ± 0.4 kJ/mol at xSn = 0.45). The calculations are performed using the geometric and analytical Redlich–Kister–Muggianu models of ΔH for melts of the ternary Gd–Sn–Ni system from similar data for binary boundary subsystems at 1873 K. The results show the minimum enthalpy of mixing of these ternary melts was established for the Gd0.55Sn0.45 alloy. It is shown that the experimentally investigated enthalpies of mixing of the Gd–Sn–Ni melts and calculated data using the Redlich–Kister–Muggianu model with ternary interaction parameter L = 500 kJ/mol agree satisfactorily with one another.

Isoperibolic calorimetry is used to specify the partial and integral mixing enthalpies of liquid Al–Ti(Zr, Hf) alloys at 1770 ± 5 K and 1790 ± 5 K. The concentration dependences of the mixing enthalpies of Al–Hf alloys are determined for the first time for 0 < x Hf < 0.2 at 1790 ± 5 K and relevant quantities are modeled for the entire concentration range. The data show that the mixing enthalpies of Al–Ti melts depend on temperature. The values of ΔS and ΔG are calculated for Al–IVb metal melts.

By the method of calorimetry in isoperibolic conditions are determined integral and partial mixing enthalpies of liquid alloys of the Ni-Hf system at 1770 ± 5 K. Defined that liquid Ni-Hf alloys are formed with allocated large quantity of heat. The analysis of own and literary data has allowed to establish for mixing enthalpies of binary Ni-Hf liquid alloys dependence on temperature. With use of the Schröder equation are calculated the activities of studied alloys components from co-ordinates of liquidus line of the phase diagram of this system. Between calculated and experimentally established values of melts components activities of the Ni-Hf system is observed only qualitative consent. Are also calculated ΔG and ΔS of liquid Ni-Hf alloys.