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536.653:546.56′82We have used solution calorimetry at temperatures of 1573 K and 1873 K over broad concentration ranges to study the mixing enthalpy of Cu − Ti liquid alloys. The molar mixing enthalpies of the system are significant negative values. We have established the temperature dependence of the molar mixing enthalpies of the system: there is an increase in their exothermicity as the temperature is lowered. The significant negative mixing enthalpies of the system allow us to conclude that the chemical bonds are localized in the studied melts and consequently associates form. We tested this conclusion within ideal associated solution theory, which describes well the results obtained with a set of CuTi and CuTi 2 associates. Using the model obtained, we have calculated the excess thermodynamic functions of mixing (enthalpy, Gibbs free energy, heat capacity) for the liquid alloys. We estimated the Gibbs energies of fcc, bcc, and hcp solutions in the system by the CALPHAD method, using data from the initial sections of the phase diagrams and from the corresponding thermodynamic data. We have calculated the metastable phase equilibria between the limiting solid solutions and the liquid or supercooled liquid phase. It was shown that for the supercooled liquid and the amorphous phase, a broad concentration range of relative thermodynamic stability can be obtained. The concentration range of amorphization of Cu − Ti melts corresponds to the position of the metastable liquidus line and the T 0 line at temperatures close to the temperature range of amorphous solidification.The thermodynamic properties of liquid copper − titanium alloys are interesting especially in connection with the possibility of obtaining two-component metallic glasses in this system by quenching from the liquid [1-4] and the prospects for using this system as the basis for development of multicomponent compositions with low critical glassforming rates [5,6]. The possibility of melts passage in the system to the amorphous state can not be explained without analyzing the nature of the temperature-composition dependence of thermodynamic properties of competing phases. Furthermore, data on the thermodynamics of the process of copper and titanium alloy formation is limited and ambiguous.The formation enthalpies of liquid alloys of copper and titanium have been studied by calorimetric methods [7][8][9]. In [7,8], the integral mixing enthalpies of solid titanium with liquid copper were studied at 1373 K in the composition range 0.01 < x Ti < 0.70. Using these data, in [8] the integral mixing enthalpies were calculated for supercooled liquid titanium (Fig. 1a). The values of the first mixing enthalpy of titanium were found: −7.65 kJ/mole [7] and −9.0 kJ/mole [8], and also the minimum of integral mixing enthalpy: -3.8 kJ/mole [8].In [9], the partial mixing enthalpy of titanium with copper was studied in the composition range x Ti = 0-0.55 at a temperature of 1873 K. These data were obtained by recalculating the experimentally determined partial enthalpi...

669.35:536.717 Thermodynamic evaluation of the Cu-Ni system within the CALPHAD approach is based on values of mixing enthalpies and activities of components in liquid and solid solutions, as well as parameters of phase transformations. The excess Gibbs free energy of phases is described by the following equations:mole for liquid alloy and ΔG (Cu, Ni), ex = x Ni (1 -x Ni )× × (6877.12 + 4.6T + (1-2x Ni )(-2450.1 + 1.87T)) J/mole for fcc solution. For the Gibbs free energy of the (Cu, Ni) phase, the magnetic effect is described by the Hillert-Jarl method. The thermodynamic model of the system generates a self-consistent description of all thermodynamic values and phase equilibria. The calculated binodale of fcc solid solution is in satisfactory agreement with experimental data. The critical point have coordinates 605 K and x Ni = 0.6.Binary copper-nickel alloys and more complex composites based on them have important mechanical and electrical properties and demonstrate high corrosion resistance in different environments. That is why they are widely used in contemporary industry as structural and electrotechnical materials. Therefore, studying the interaction of copper and nickel is an important task. Processes for extracting these valuable metals from secondary raw materials are another significant application. In this regard, the phase diagram of the system and thermodynamic properties of its phases attracted the close attention of experimenters and were repeatedly subjected to thermodynamic modeling. However, the published data on thermodynamic mixing functions demonstrate substantial differences both in the absolute value and temperature dependence, and phase equilibria in the low-temperature region cannot be considered fully understood. PHASE EQUILIBRIA IN THE SYSTEMThe system components show complete liquid and solid miscibility. Hence, there are two phases in equilibrium: liquid L and fcc solution (Cu, Ni). The existence of the solid solution was confirmed with optical microscopy and x-ray examination. The solidus and liquidus lines form a cigar-shaped phase diagram with a narrow two-phase region. Different research teams invariably arrived at similar conclusions. The results of research efforts up to 1958 were analyzed in [1].Contemporary studies of the phase equilibria in the system [2][3][4][5] focus of the positioning of the liquidus and solidus lines (Figs. 1 and 2). The papers [2, 3, 5] used for this purpose an x-ray spectral microanalysis of samples quenched from the two-phase region. In addition, the paper [3] established the position of the liquidus line with a thermal analysis followed by extrapolating the data to the zero cooling rate. The measurements made in [3] cover the entire concentration range, the data from [2] the region of copper-rich alloys, and the data from [5] alloys with x Ni < 0.30 and x Ni > 0.70. The paper [4] studies the phase equilibrium between the liquid and solid solutions with a thermal analysis of seven alloy compositions in the range x Ni = 0.01-0.87.Donbass State Mech...

The cohesive energy of transition metals and its contributions related to the s-and d-electrons are calculated. The correlation of interatomic bonding strength, molar volume, and compressibility of transition metals with cohesion energy and corresponding contributions to it is shown. It is demonstrated that the s-electrons play an important part in the cohesion of transition metals. The main contributions to the formation energy of disordered alloys of copper with transition metals are calculated using the tightbinding approach. The results obtained are in qualitative agreement with experimental data on the thermodynamic properties of Cu-3d-metal systems.In condensed state, atoms are held together by cohesive forces, which are the total forces exerted by an atom on its nearest neighbors. In most cases, it is very difficult to measure these forces because ultimate strength and elastic limit depend on the imperfection of samples in mechanical tests. Therefore, various physical properties associated with the cohesive forces and characterizing, in a way, the strength of interatomic bonds in a crystal are used as measures of these forces among atoms in a crystal lattice. These characteristics include various thermodynamic, elastic, and thermal constants of which the most important are sublimation heat, atomization energy, melting point, elastic modulus, Debye characteristic temperature, and thermal expansion coefficients [1].Since elucidating the physical and chemical nature of interatomic interaction and cohesive forces in transition metals and their alloys is of great importance for developing the theory of condensed phases and modern physical metallurgy, it appears expedient to try to asses their cohesive energy within the available chemical binding models. COHESIVE ENERGY AND PROPERTIES OF TRANSITION METALSIt was shown in [2−4] that the cohesive energy of transition metals is high due to the band energy of d-electrons and that the change of the energy along transition series may be associated with increased filling of the d-band. According to [2,4,5], the tight-binding model uses simple summation of one-electron cohesive energies to calculate the cohesive energy of a transition metal due to overlapping of d-electrons:where E d is the cohesive energy due to d-electrons; E f is the Fermi energy reckoned from the conduction-band bottom; E d is the energy of the atomic d-level spreading into a band of finite width W d ; B d is the energy of the d-band bottom; and n d (E) is the density of electron states in the d-band.Thus, to calculate the cohesive energy of transition metals and their alloys, it is necessary to know the density of electronic states n d (E) in the d-band. In the general case, the function n d (E) has a complicated form (there are minima Donbass State Mechanical Engineering Academy, Kramatorsk.

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