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 determine the enthalpies of mixing of liquid alloys of the Ag‒Al–Yb system along two radial sections with a constant ratio of atomic fractions of aluminum and silver: (1) xAg/xAl = 0.46/0.54 at 1271 ± 1 K and (2) xAg/xAl = 0.19/0.81 for 1454 ± 5 K up to xYb ∼ 0.2. It is found that melts of the studied system form with the release of a small amount of heat (ΔHmin = −29 kJ/mol), and the minimum ΔH accounts for the middle of the concentration triangle. Using the geometric and analytical Redlich–Kister models, calculations are made for ΔH triple system melts Ag–Al–Yb using similar data for double boundary subsystems.

The mixing enthalpies of Sr–Sb melts were measured by isoperibolic calorimetry at 1230 K over the entire composition range referred to the liquid components. Large exothermic mixing effects were found (∆Hmin = –70.1 ± 4.8 kJ/mole). They were indicative of very strong interaction between the components and agreed with the Sr–Sb phase diagram. A series of intermetallic compounds, SrSb, SrSb3, Sr3Sb2, and Sr2Sb, was found in the system. Minimum ∆H for the liquid alloys corresponds to the composition range where SrSb and Sr3Sb2 phases exist. The mixing enthalpies were found to be less exothermic than those for the intermetallic phases. This finding agrees with data for the alloys in systems with strong interaction between the components and is indicative of short-range ordering in liquid state. The mixing enthalpies for Mg (Ca, Sr)–Sb melts decrease in the Mg–Sb → Ca–Sb → Sr–Sb series, which agrees with increasing differences in the electronegativity of the components.

The thermochemical properties of binary Ba–In melts were studied using calorimetry at 1070–1320 K over a wide composition range. It is shown that these melts are characterized by significant exothermic heat effects of mixing. The ideal associated solution model was used to calculate the activities of components, Gibbs energies, and mixing entropies of the alloys and to construct the liquidus curve in the phase diagram. These parameters agree with the literature data.

Mixing enthalpies of melts of the Ge–La system have been measured using isoperibolic calorimetry within two concentration ranges. For the first range (0 < x La < 0.16 at 1520 K and 0.16 < x La < 0.29 at 1570 K), agreement with the known literature data is observed within the experimental error. The second range (0.78 < x La < 1 at 1470 K and 0.7 < x La < 0.78 at 1580 K) has been studied for the first time. The melts are characterized by very strong exothermal effects of mixing, which have almost symmetrical concentration dependence: ΔH̅ La ∞ = ΔH̅ Ge ∞ = −245 kJ/mol at 1470 K. A thermodynamic optimization of the activities of the components and the phase diagram of the system have been conducted based on the obtained experimental data, using an ideal associated solution (IAS) model.

Mixing enthalpies of alloys in the Cu–La system are measured using isoperibolic calorimetry method over the ranges 0 < x La < 0.185 at 1400–1430 K and 0.659 < x La < 1 at 1370 K. They have moderate exothermic values over the whole concentration range and agree with literature data. Activities of the components, enthalpies and entropies of formation of intermetallics in this system, and its phase diagram are optimized using an ideal associated solution (IAS) model, and agree with most literature data. The updated thermodynamic properties can be used in further investigation of multicomponent systems based on the binary Cu–La.

The partial mixing enthalpy of aluminum and the integral mixing enthalpies of liquid alloys in the binary Al–Co system are studied by high-temperature calorimetry at 1870 ± 5 K in the composition range 0 < x Co < 0.25. The energies of forming alloys of aluminum with metals in the second half of the 3d series are compared.

The mixing enthalpies of liquid binary In–Ni alloys (0.85 < x Ni < 1) at 1800 K were determined by isoperibol calorimetry. The thermodynamic properties of the In–Ni alloys were calculated for the entire composition range using the model of ideal associated solutions. The thermodynamic activities of melt components show negative deviations from the ideal behavior. The mixing enthalpies are characterized by moderate exothermic effects. The minimum mixing enthalpy of the melts is –12.0 ± 0.1 kJ/mol at x Ni = 0.59.

The enthalpies of mixing for liquid alloys of the Ag-Sm system are determined by isoperibolic calorimetry at 1450–1506 K in the 0.46 < x Sm < 1 range of concentrations. The partial and integral enthalpies of mixing for melts of the Ag-Sm system are obtained over the whole range of concentrations. The activities of components and the entropy of mixing in melts of the Ag-Sm system at 1506 K are calculated using a model of ideal associated solutions (IAS). The partial and integral enthalpies of mixing for melts of the Ag-Sm system, the activities of the components, and the molar fractions of associates in them are calculated using the IAS model. It is concluded that the thermodynamic activities of components in melts of the Ag (Au)-Sm system at 1506 K exhibit great negative deviation from the ideal behavior, and the enthalpies of mixing indicate there are considerable exothermal effects.