Showing papers in "Journal of Phase Equilibria in 1996"
TL;DR: In this paper, a low-temperature Fe-Ni phase diagram is presented, which is consistent with the available theoretical diagram in that α/Ni3Fe equilibrium was found at low temperatures.
Abstract: The low-temperature Fe-Ni phase diagram was assessed experimentally by investigating Fe-Ni regions of meteorites using high resolution analytical electron microscopy techniques. The present phase diagram differs from the available experimental phase diagram based on observations of meteorite structure, but it is consistent with the available theoretical diagram in that α/Ni3Fe equilibrium was found at low temperatures. The a phase containing 3.6 wt.% Ni is in local equilibrium with the γ′ (Ni3Fe) phase containing 65.5 wt.% Ni, while the γ′' (FeNi) phase is present as a metastable phase. The new phase diagram incorporates a monotectoid reaction (γ1 → α + γ2, where (γ1 is a paramagnetic fcc austenite, a is a bcc ferrite, and γ2 is a ferromagnetic fcc austenite) at about 400 °C, a eutectoid reaction (γ2 → α + γ′) at about 345 °C, and a miscibility gap associated with a spinodal region at low temperatures. The miscibility gap is located between 9.0 and 51.5 wt. % Ni at ∼200 °C. The new low-temperature Fe-Ni phase diagram is consistent with all the phases observed in the metallic regions of meteorites.
183 citations
166 citations
TL;DR: In this article, the condensed Ti-C system was assessed using a computerized least squares optimization method, and the solid phases were modeled as interstitial solid solutions or by the compound energy formalism with two sublattices, respectively.
Abstract: The condensed Ti-C system was assessed using a computerized least squares optimization method. The solid phases—αTi, βTi, and TiC—were modeled as interstitial solid solutions or by the compound energy formalism with two sublattices, respectively. The liquid phase was described by a Redlich-Kister polynomial. All phase diagram data and thermodynamic values available in the literature were critically assessed before the optimization. An optimized thermodynamic parameter set is presented, and the resulting calculations are compared with experimental and estimated data from the literature.
79 citations
TL;DR: In this paper, the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature were evaluated for all phases in the CrO-Cr2O3, CrO -Cr 2O3-CaO, Cr 2O 3 -Al2O 3, Cr 2 O 3 -CaO and Cr O 2 O 2 -Al 2 Al2 O 3 systems.
Abstract: Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr2O3, CrO-Cr2O2-Al2O3, and CrO-Cr2O2-CaO systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air in the case of the first two systems and toP
O
2 = 10−3 atm for the CrO-Cr2O3-CaO system. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasichemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.
64 citations
TL;DR: In this article, a revised Ni-Nb (nickel-niobium) phase diagram with realistic enthalpy of formation values for the intermetallic phases that compare with experimental values is presented.
Abstract: A revised calculation of the Ni-Nb (nickel-niobium) phase diagram includes realistic enthalpy of formation values for the intermetallic phases that compare with experimental values, a more accurate crystallographic description of the μ phase, and a better fit to the experimentally determined invariant equilibrium temperatures and liquidus-solidus boundaries between liquid and (Ni). The set of parameters describing the Gibbs energy of each phase is given.
61 citations
TL;DR: The Margules equation as discussed by the authors is an important basic equation of thermodynamics, which yields an elegant formulation of the laws of Raoult and Henry, and its relationship with theoretical equations are briefly discussed.
Abstract: The Margules equation, which is in accord with the GibbsDuhem relation, is an important basic equation of thermodynamics. It yields an elegant formulation of the laws of Raoult and Henry. Its relationships with theoretical equations are briefly discussed. The Margules equation should also be applicable to the ionic solutions if it can represent any other equation capable of representing the excess partial Gibbs energy of a solution.
45 citations
TL;DR: In this article, enthalpies of formation of Ni3Al in the L12 structure ranging from −41.3 to −42.3 kJ/mol were determined at temperatures from 300 to 1123 K.
Abstract: Using Al solution calorimetry, enthalpies of formation of Ni3Al in the L12 structure ranging from-41.3 to -42.3 kJ/mol were determined at temperatures from 300 to 1123 K. These enthalpies are substantial for an intermetallic compound and display a slight temperature dependence, which is contained within the experimental error. This temperature dependence is related to the lack of any transformations of the compound, which remains ordered up to the melting temperature. The measured enthalpies were combined with other thermodynamic data to estimate the excess entropy of formation of Ni3Al. The high degree of ordering in the compound is reflected in the large negative value of the excess entropy,whose absolute value exceeds those for other high melting temperature intermetallic compounds. The full-potential linearized augmented Slater-type orbital method (FLASTO) was used to calculate the enthalpies of formation of paramagnetic and ferromagnetic Ni
3Al. These enthalpies of formation indicate the compound to be a weak ferromagnet, and they are in good agreement with the calorimetric data.
45 citations
TL;DR: In this paper, a computer-operated least squares method applied to all of the experimental phase diagram and thermodynamic data from the literature is applied to obtain consistent sets of thermodynamic functions for the Al-Ta system.
Abstract: Consistent sets of thermodynamic functions for the Al-Ta system are obtained by a computer-operated least squares method applied to all of the experimental phase diagram and thermodynamic data from the literature Special attention is paid to the σ phase, AlTa2, which is described by a sublattice model, (Al,Ta)10Ta4(Ta,Al)16, in a final treatment The other phases are modeled with the Redlich-Kister formula [liquid, fcc (Al), and bcc (Ta)] or as stoichiometric compounds (Al3Ta, Al69Ta39, Al3Ta2, Al7Ta5, and AlTa) Four treatments are performed In the first and second treatments, which differ by whether or not the experimental partial Gibbs energy data of Al in bcc (Ta) are used, AlTa2 is assumed to be a stoichiometric compound; in the third and final ones, it is described by sublattice models (Al,Ta)1Ta2 and (Al,Ta)10Ta4(Ta,Al)16, respectively Data on the partial Gibbs energy of Al in bcc (Ta) are not consistent with solid solubility data of Al in bcc (Ta) In the second, third, and final treatments, this step-by-step modeling procedure provides reliable estimates and useful starting values for the parameters at each of the higher levels In addition, the complete and consistent thermodynamic functions of the second or third treatments may be useful for a simplified description of the Al-Ta system if less accuracy for the σ phase is required A comparison with other σ phase descriptions in the literature suggests some benefits of the model used in the final treatment It covers a broad composition range It is supported by the crystal structure, and it uses a small number of adjustable parameters
40 citations
TL;DR: Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) measurements provide phase diagram data in the whole composition range, and an optimization and calculation study was done to generate the thermodynamic functions of each phase as mentioned in this paper.
Abstract: Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) measurements provide phase diagram data in the whole composition range. From the results and literature data, an optimization and calculation study was done to generate the thermodynamic functions of each phase.
36 citations
TL;DR: In this article, the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature were evaluated for all phases in the CrO-Cr2O3-SiO2 and CrO -Cr 2 O3-Al2O2-Al 2O3 systems from 298 K to above the liquidus temperatures.
Abstract: Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.
TL;DR: In this paper, phase diagrams and thermodynamic properties of the Cu-R (R: Ce, Pr, Nd, Sm) systems are reevaluated on the basis of all available experimental data, including the enthalpies of mixing reported recently.
Abstract: The phase diagrams and thermodynamic properties of the Cu-R (R: Ce, Pr, Nd, Sm) systems are reevaluated on the basis of all available experimental data, including the enthalpies of mixing reported recently. The Redlich-Kister polynomial with two or three terms is used to describe the excess Gibbs energies of liquid phases in the Cu-R systems. All intermediate phases are treated as stoichiometric, and their Gibbs energies of formation are optimized. Based on the optimized thermodynamic parameters, phase diagrams and thermodynamic properties of the Cu-R systems are calculated and compared with the experimental results. The optimized parameters seem to be in good agreement with the experimental data and might represent the regularity and systematic variation of these systems.
TL;DR: In this article, the 450 °C isotherm of the Zn-Fe-Al ternary phase diagram has been revised based on the findings in a number of recent studies.
Abstract: The 450 °C isotherm of the Zn-Fe-Al ternary phase diagram has been revised based on the findings in a number of recent studies. The Γ′ phase was included as an equilibrium compound in the system, the boundaries of the ζ, δ, Γ′, and Γ′ phases were more accurately outlined, and the invariant of the ι-η-θ three phase equilibrium has been placed at 1.3%A1 on the liquid phase boundary.
TL;DR: In this paper, a thermodynamic criterion for identifying the symmetry of ternary systems (from energy-asymmetry) is proposed after having been successfully tested on a large number of molten salt and alloy systems.
Abstract: Based on previous significant and enlightening studies in the literature and on thermodynamic considerations, a thermodynamic criterion for identifying the symmetry of ternary systems (from energy-asymmetry) is now proposed after having been successfully tested on a large number of molten salt and alloy systems. After a systematic comparison was made of calculated phase diagrams and excess thermodynamic properties with experimentally measured ones, it can be concluded that in using geometric models to predict ternary thermodynamic properties from subbinary systems, the key point is to choose a reasonable symmetric or asymmetric model noting that in most cases the main source of error in prediction arises from misjudging the asymmetric component in the asymmetric geometric model. This is of great significance in improving the calculated accuracy when predicting the thermodynamic properties of a ternary solution phase from data for the subbinary systems.
TL;DR: The Nd-Fe-B binary phase diagram was constructed using contributions from a number of sources as discussed by the authors, including the B-Sm system, and the liquid, liquid, and terminal solid solution, with negligible solubility for Nd.
Abstract: Given the scientific and commercial significance of the ternary Nd-Fe-B system, it is surprising that so little is known about the Nd-B binary phase diagram. Figure 1, the assessed Nd-B diagram, was constructed using contributions from a number of sources. The diagram is similar to that for the B-Sm system. Its phases include the liquid, L; the two stable neodymium allotropes, (txNd) and ([3Nd), each with negligible solid solubility ranges; four intermetallic phases assigned the stoichiometries Nd2B 5, NdB4, NdB6, and NdB66; and the terminal solid solution, (~B), with negligible solubility for Nd. The liquidus temperatures and invariant compositions are estimated, largely based on results f0r the B-Sm system [76Spe, 77Spe].
TL;DR: In this article, the Fe-Hf-Zr phase diagram was determined at 900 °C in the Ferich corner by powder x-ray diffraction (XRD) and electron probe microanalysis (EPMA).
Abstract: The Fe-Hf-Zr phase diagram was determined at 900 °C in the Fe-rich corner by powder x-ray diffraction (XRD) and electron probe microanalysis (EPMA). Iron-rich parts of the Fe-Hf and Fe-Zr binary systems were also reviewed. The existence of Fe23Zr6 with a cubic Mn23Th6 structure was confirmed. A calorimetric study by direct reaction at high temperatures gave the enthalpies of formation of Fe23Zr6, Fe0.70Hf0.30(λ), and some ternary alloys: Fe0.66(Hf, Zr)0.34 and Fey(Hf, Zr)l-y with 76≤y≤100at.%Fe.
TL;DR: A revised version of the germanium-ruthenium (Ge-Ru) equilibrium phase diagram was obtained by differential thermal analysis (DTA), x-ray diffraction (XRD), and microprobe investigations as discussed by the authors.
Abstract: A revised version of the germanium-ruthenium (Ge-Ru) equilibrium phase diagram was obtained by differential thermal analysis (DTA), x-ray diffraction (XRD), and microprobe investigations. The two compounds, GeRu (melting point, 1510 ± 5 °C) and Ge3Ru2 (melting point, 1551 ± 5 °C), are congruently melting and form a eutectic at 1488 ± 3 °C (47 at. % Ru). The solid solubility of Ge in (Ru) is negligible at room temperature, and that of Ru in (Ge) is not noticeable.
TL;DR: In this paper, the Ag-Sn binary system was reoptimized because of the increasing interest in lead-free solder development and the ordered semistoichiometric Ag3Sn phase was described as a line compound while the other phases were represented by Redlich-Kister expressions.
Abstract: The Ag-Sn binary system is reoptimized because of the increasing interest in lead-free solder development The ordered semistoichiometric Ag3Sn phase is described as a line compound while the other phases are represented by Redlich-Kister expressions Results are compared with previous efforts, and the agreement between the calculated phase diagram and the assessed phase boundary data has been significantly improved while reproduction of experimental data for thermodynamic properties remains excellent
TL;DR: In this paper, the Zn-Se phase diagram is reanalyzed with an associated solution model for the liquid, new Se-rich liquidus points, and a new Gibbs energy of formation for ZnSe(s).
Abstract: The Zn-Se phase diagram is reanalyzed with an associated solution model for the liquid, new Se-rich liquidus points, and a new Gibbs energy of formation for ZnSe(s). After the liquid model parameters are fixed by a best fit to the liquidus points, the entire liquidus is generated as well as the partial pressures of Zn and of Se2 along the ZnSe(s) three-phase curve, isotherms for the enthalpy of mixing, and the isotherm for the activity coefficients at the 1799 K melting point of ZnSe(s).