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 thermodynamic assessment of the Cu-Zr and Ti-Zr systems is carried out using the CALPHAD method. The Gibbs energy of Cu-Zr liquid alloys is described by the ideal associated solution model. The excess Gibbs energy of Ti-Zr liquid alloys and Cu-Zr and Ti-Zr solid solutions is descried by models with Redlich-Kister polynomials. The Gibbs energy of Cu-Zr intermetallic compounds is described by models taking into account their formation enthalpy and entropy. A set of self-consistent parameters of the models is obtained using data on phase equilibria and thermodynamic properties of the phases. The calculated phase diagrams of the systems and values of thermodynamic properties of the phases are in good agreement with experimental information. The relative thermodynamic stability of supercooled liquid alloys and competitive crystal phases of the Cu-Zr system are analyzed.

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The CALPHAD method is used for the thermodynamic assessment of the Cu-Ti system that bounds the ternary Cu-Ti-Zr system, which is capable of forming amorphous alloys. The self-consistent parameters of thermodynamic models of the phases are obtained from data on the phase equilibria and thermodynamic properties of liquid alloys and intermetallic compounds. The Gibbs energy of the liquid phase is described using the associated ideal solution model. To describe the thermodynamic properties of the Cu 4 Ti and CuTi intermetallic compounds with homogeneity range, sublattice models are used. The calculated phase diagram of the system and the thermodynamic properties of the phases are in good agreement with experimental data.

The work's purpose is to increase the forging ingot's quality. A crystallization mechanism of shortened ingots has been investigated. The shortened ingots allow changing a direction of the metal solidification. The rational geometry of the ingot (a ratio of height to diameter and a value of taper) needs to be determined. The special technique of the theoretical and experimental investigations has been developed. The theoretical investigations have been carried out by finite element method. An adequacy test of the theoretical results has been carried out by experimental investigations on transparent and metallic models (pure aluminum) of the ingots. The macrostructure investigations of the shortened ingots with directional solidification have been produced. A hardness distribution on the longitudinal section has been investigated. It was found that for the ingot with the ratio of H/D = 1.1 the most part of the ingot's body (60-70%) has a dense, homogeneous and small-grained structure. The small grain, which provides a dense structure, forms at the bottom and in the corners from the bottom side. The distribution of the grain dimensions along the ingot radius at different height levels allows to conclude that the bottom and middle parts along the height have the same small-grained structure. The high and uniform hardness values are characteristic for the ingot with H/D = 1.1. The middle and hot-top layers of the ingot have commensurate hardness, which have a difference from the bottom part maximum on the 5%. The ingot with the reverse taper of 7% allows to make a most dense and homogeneous structure. Thus, the improvement in the large forged quality ingots is possible by providing the directional solidification and reverse taper.

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The mixing enthalpies of ternary Cu-Fe-Co liquid alloys are studied by the calorimetric method at 1873 K and x Co = 0-0.55. Thermodynamic assessments of the Fe-Co and Cu-Fe-Co systems are carried out with the CALPHAD method. A set of self-consistent thermodynamic parameters of the phases is obtained using data on the mixing enthalpies established in this study and published information on phase transformations. Isothermal and vertical sections of the phase diagram, liquidus and solidus surfaces, and metastable miscibility gap for overcooled liquid alloys are calculated. The undercooling degrees for the metastable liquid phase separation and temperaturecomposition ranges of the formation of the supersaturated solid solutions during the liquid quenching have been assessed.