A thermodynamic evaluation of the FeMoC system

A new evaluation of the Fe-Mo-C system has been made using a sublattice model and including the magnetic effect. A set of parameter values describing the Gibbs energy of each individual phase was determined with a computerized optimization technique. It gives satisfactory agreement with the experimental information over a wide temperature range. Several diagrams and tables concerning phase equilibria are presented.     

Calculation of thermodynamic properties of LiFAlF3, NaFAlF3 and KFAlF3

The scheme of dissociation of cryolite in NaFAlF₃ melts is proposed and applied to the LiFAlF₃ and KFAlF₃ systems. The constants and enthalpies of dissociation for alkali-cryolites are evaluated from experimental data. The mole fractions of each proposed species at 1298K in these three melt systems are calculated, and the variation of alumina solubility in alkali-cryolite can be explained on the basis of the ionic structure for the MF- AlF₃ (M: Li, Na and K) melts. The thermodynamic properties and liquidus data of MF-AlF₃ systems are calculated by using the selected evaluated parameters. Some results are compared with experimental values.     

Calculation of the FeZnSi phase diagram between 773 and 1173 K

The phase diagram for the Fe-Zn-Si system has been calculated from thermodynamic data for the binary systems. The excess Gibbs energies of the solid and liquid solutions in the ternary system are described by: ΔG^xs = ΔG^xs₁₂ + ΔG^xs₁₃ + ΔG^xs₂₃ + ΔG^xs₁₂₃ with: ΔG^xs_ij = x_ix_j(A_ijx_i + B_ijx_j)ΔG^xs₁₂₃ = A₁₂₃x₁x₂x₃ The ternary interaction parameter A₁₂₃ is obtained from experimental characteristics of the ternary diagram: temperature dependance on the solubility of Zn in Fe₃Si and FeSi in Zn. The diagram Fe-Zn-Si calculated between 773 and 1173 K is used for explaining diffusion path observed during galvanization of the Fe-Si alloys.     

Application of the Hoch-Arpshofen model to the SiO2CaOMgOAl2O3 system

The Hoch-Arpshofen model was applied to the SiO₂-CaO-MgO-Al₂O₃ system. First the binary interaction coefficients, obtained from the six binary systems, were used to calculate the Gibbs energy of formation of the ternary compounds present in the four ternary systems; then the calculated activities of SiO₂, CaO, and Al₂O₃ were compared with the measured activities. The calculated Gibbs energies of formation of anorthite, gehlenite, and cordierite agree with the measured energies; the measured enthalpies of formation of akermanite, diopside, merwinite, and monticellite must be multiplied by 0.568 ± 0.031 to obtain agreement. The Gibbs energy of formation of 3CaO-MgO-2Al₂O₃ was also calculated. The calculated activity data agree with some authors' measurements and not with others.     

Thermodynamic optimization of the Mn–P and Fe–Mn–P systems

Thermodynamic modeling of the Mn–P and Fe–Mn–P systems in the full composition was carried out using the CALculation of PHAse Diagrams (CALPHAD) method based on the critical evaluation of all available phase equilibria and thermodynamic data. The liquid and solid solutions were described using the Modified Quasichemical Model and Compound Energy Formalism, respectively. The Gibbs energies of the binary stoichiometric iron and manganese phosphides were determined based on reliable experimental data. The ternary (Fe,Mn)₃P, (Fe,Mn)₂P and (Fe,Mn)P phosphides were modeled as solid solutions with mutual substitution between Fe and Mn atoms. The Gibbs energy of the liquid solution was predicted using the Toop interpolation technique with P as an asymmetric component, without any ternary parameters. The thermodynamic properties of P in the entire composition region and the liquidus of the ternary system were well reproduced. Based on the thermodynamic models with optimized parameters, unexplored phase diagrams and thermodynamic properties of the Fe–Mn–P system were predicted.     

Thermodynamic study of the KMgAlClSO4H2O system at the temperature 298.15 K

The Pitzer ion-interaction model has been used for thermodynamic simulation of the binary AlCl₃H₂O, Al₂(SO4)₃H2O, ternary KClAlCl₃H₂O, K₂SO₄Al₂(SO₄)₃H₂O, MgCl₂AlCl₃H₂O, MgSO₄Al₂(SO₄)₃H₂O, and the quaternary KClMgCl₂AlCl₃H₂O systems at T=298.15 K. The optimum values of the binary parameters of ionic interactions for aluminum solutions have been calculated using activity data up to saturation of solutions. The ternary parameters have been chosen on the basis of the compositions of saturated ternary solutions taking into account the unsymmetrical mixing terms. Good agreement between experimentally determined and calculated solubilities has been found. Important thermodynamic characteristics (thermodynamic solubility product, standard molar Gibbs energy of formation) of the solid phases (simple and double salts) crystallizing in the systems under consideration are determined.     

Thermodynamic modeling of the ZrO system

In this study, the complete zirconium-oxygen system has been critically assessed at 1 at. from 300°C to liquidus temperatures. Thermochemical measurements and phase diagram data were used to model the Gibbs free energies of seven phases. Additionally, the ordered interstitial HCP-based solutions were included and considered as simple line compounds. By using the PARROT module in Thermo-Calc, it was possible to optimize the parameters of the models used to describe the Gibbs free energies of the HCP, BCC, Liquid, γ ZrO_2−x,β ZrO_2−x and α ZrO_2−x phases. The Gas phase was considered to behave ideally. Although phase diagrams including the stoichiometric zirconia phases have been assessed, this is the first time, to the best of our knowledge that a complete assessment of this system is published.     

A Thermodynamic description and phase relationships of the FeCr system: Part II the liquid phase and the fcc phase

The high-temperature thermodynamic data and phase equilibria of the FeCr binary reported in the literature are assessed. A set of thermodynamic values for the liquid, bcc and fcc phases are obtained. These values are internally consistent and the calculated phase equilibria are in agreement with the measured phase boundary data. Metastable equilibria for the liquid and fcc phases are also calculated.     

A thermodynamic description and phase relationships of the FeCr system: Part I the BCC phase and the sigma phase

A generalized approach which was applied successfully to account for the magnetic contribution to the thermodynamic properties of FeNi is applied to FeCr. The predicted magnetic specific heats for two bcc alloys at x_Cr = 0.16 and 0.21 are in good agreement with the experimental data available in the literature. The magnetic Gihbs energy, enthalpy and entropy for the bcc phase are obtained accordingly. The nonmagnetic thermodynamic properties of the bcc phase are obtained primarily from thermochemical data as well as those for the sigma phase. The calculated stable and metastable equilibria involving the bcc and sigma phases are in reasonable agreement with data reported in the literature. The calculated metastable miscibility gap of the bcc phase is highly asymmetric and the calculated spinodals show unusual features.     

Thermodynamic reassessment of the Y 2O3–Al2O3–SiO2 system and its subsystems

Phase equilibria and thermodynamic properties at 1 bar in the Y ₂O₃–Al₂O₃–SiO₂ ternary system and its constituent binaries Y ₂O₃–Al₂O₃ and Y ₂O₃–SiO₂ have been reevaluated using the CALPHAD approach. The liquid phase is described by the ionic two-sublattice model with the formula (Al⁺³,Y ⁺³)_P(AlO₂⁻¹,O⁻²,SiO₄⁻⁴,SiO₂⁰)_Q. The SiO₂ solubility in the YAM phase was described using a compound energy model. Two datasets of self-consistent model parameters are presented. However, the rather meagre and scattered experimental data imply that the present assessments should be regarded as provisional. Some critical experiments are suggested for this system.