W. Zakulski

Thermodynamic studies and the phase diagram of the Li-Mg system

By means of the electromotive force (emf) method of concentration cells of the following scheme: Li (1) / LiCl-LiF (eut) or LiCi-KCl (eut) / Li-Mg (1) or Li (1) / LiCl-LiF (eut) / Li-Mg (s) Li activities for liquid and solid alloys at the (Mg), (Li), and (Mg) + (Li) two-phase region of the Li-Mg system were determined. Liquid alloys were examined at temperatures from 638 to 889 K at various Li concentrations. The (Mg) solid solutions were investigated in two series: at constant temperatures between 773 and 876 K, with varying Li content, and at fixed Li concentrations, equal to 0.125 and 0.160 molar fractions, at different temperatures between 772 and 849 K. At the two-phase region, (Mg) + (Li), emf measurements were performed in the temperature range 773 to 838 K, with fixed Li concentrations equal to 0.20, 0.25, and 0.275 molar fractions. For (Li) solid alloys, experiments were done at temperatures 773 to 849 K for several constant Li concentrations, between 0.30 to 0.45 molar fractions, respectively. Studies on solid alloys enabled us also to determine the boundaries (Li)/[(Mg) + (Li)] and (Mg)/[(Mg) + (Li)] at temperatures 773 to 831 K. The resulting thermodynamic and phase boundary data of this study were used with other selected references for a critical assessment of the Li-Mg system. The Lukas BINGSS optimization program and BINFKT for the calculation of the thermodynamic functions and of the phase diagram were used. The calculated equilibrium phase diagram at temperatures below 750 K indicates a slightly lower solid solubility of Mg in (Li) in comparison with results from thermal analysis and the recently published Saunders evaluation.

Thermodynamic studies and the phase diagram of the Li-Sn system

By means of the electromotive force (emf) method of concentration cells of the following scheme: Li (1) / LiCl-LiF (eut) or LiCi-KCl (eut) / Li-Mg (1) or Li (1) / LiCl-LiF (eut) / Li-Mg (s) Li activities for liquid and solid alloys at the (Mg), (Li), and (Mg) + (Li) two-phase region of the Li-Mg system were determined. Liquid alloys were examined at temperatures from 638 to 889 K at various Li concentrations. The (Mg) solid solutions were investigated in two series: at constant temperatures between 773 and 876 K, with varying Li content, and at fixed Li concentrations, equal to 0.125 and 0.160 molar fractions, at different temperatures between 772 and 849 K. At the two-phase region, (Mg) + (Li), emf measurements were performed in the temperature range 773 to 838 K, with fixed Li concentrations equal to 0.20, 0.25, and 0.275 molar fractions. For (Li) solid alloys, experiments were done at temperatures 773 to 849 K for several constant Li concentrations, between 0.30 to 0.45 molar fractions, respectively. Studies on solid alloys enabled us also to determine the boundaries (Li)/[(Mg) + (Li)] and (Mg)/[(Mg) + (Li)] at temperatures 773 to 831 K. The resulting thermodynamic and phase boundary data of this study were used with other selected references for a critical assessment of the Li-Mg system. The Lukas BINGSS optimization program and BINFKT for the calculation of the thermodynamic functions and of the phase diagram were used. The calculated equilibrium phase diagram at temperatures below 750 K indicates a slightly lower solid solubility of Mg in (Li) in comparison with results from thermal analysis and the recently published Saunders evaluation.

Thermodynamic investigations of solid CuNi and FeNi alloys and calculation of the solid state miscibility gap in the CuFeNi system

Abstract Activity values for fcc CuNi and FeNi alloys have been determined from solid electrolyte emf measurements. The results are discussed together with values reported by other investigators and evaluated data are presented for the thermochemical properties of CuNi and Fez.sbnd;Ni alloys. The evaluated data have been combined with a published assessment of the CuFe system to calculate the miscibility gap in the fee phase of the CuFeNi system.

Thermodynamic study and the phase diagram of the Mg-Sn system

By means of concentration cells of the following type, Mg (l)MgCl2 in (LiCl-KCl)eut (l)Mg-Sn (1), the partial thermodynamic data of Mg in Mg-Sn liquid solutions have been obtained in the composition range of 0.1 ≤XMg ≤ 0.75 and at temperatures from 950 to 1100 K. These values are compared with thermodynamic data reported in the literature and used for the evaluation to obtain a complete set of thermodynamic functions for phase diagram calculations and for further interpretation by the associate model. This model, which accepts the existence of ‘Mg2Sn as-sociates’ in the liquid alloys, enables calculations of viscosity by Kucharski’s method corre-lating properly with experimental data. Mutual correlations between thermodynamic properties, physical properties, structure, and the phase diagram of the Mg-Sn system were shown to in-dicate a maximum chemical short-range order close to the composition Mg2Sn.

Study of the thermal stability of phases in the Mg-Al system

A part of the Al-Mg phase diagram was studied in the range of composition between 48 and 61 at.% Al by DSC and SEM/EDS methods. The temperature ranges of stability of the β, γ, and ɛ phases were considered. It was found that the congruent melting temperature of the β phase was 450±1 °C. The Al content in that phase was determined to be 61±1 at.% Al at 420 °C. The upper temperature limit of the stability of the ɛ phase was established to be 427±1 °C. The Al content changed from 54 at.% at 390 °C to 56 at.% at 420 °C. The lower temperature limit of the ɛ phase formation was not determined, as a result of a slow ɛ=β+γ reaction. The hypothetical λ or ζ phases were not found, but it was observed that decomposition of oxides might produce extra thermal effects.

Calculation of the fcc/liquid phase equilibria in the FeCuNi system☆

Abstract Previously evaluated data for fcc CuNi and FeNi alloys together with solidus/liquidus boundaries for the two systems have been used as basis for the evaluation of the thermochemical properties of liquid alloys. The selected data for the fcc and liquid phases have been combined with an assessment of the CuFe system to calculate the fcc/ liquid phase equilibria in the FeCuNi system.

Thermodynamic studies and phase diagrams of the Cd-Ga-In system

Calorimetric and vapor pressure data of liquid Cd- Ga- In alloys were measured. From these data an optimized set of thermodynamic parameters of the Cd- Ga- In system was derived using the leastsquares method. The thermodynamic parameters of the binary subsystems were taken from the literature and combined to a ternary description by the Muggianu formula. This description was augmented by a ternary term for the liquid phase, described as a function of temperature and concentration by six coefficients.

Cd-In (cadmium-indium)

The assessed coefficients agree extremely well with existing experimental data. The liquid, fee, bet, and cph phases of the Cd-In system are satisfactorily represented by Redlich-Kister polynomial expressions to describe the Gex. G^In is best represented as a Wagner-Schottky-type, two sublattice phase where the defects are antistructure atoms, i.e., (Cd, In)o.75(In, Cd)o.25-With these descriptions, the resulting optimized coefficients for the Gex expressions reproduce the known experimental phase diagram within experimental error. There is also excellent agreement between the measured and calculated thermodynamic quantities.

A calculation of the Cd-Pb (cadmium-lead) system

The Cd-Pb system has been recalculated employing the Lukas method, taking into account the G(Cd, fcc) to G(Cd, liq) transition, fitted from experimental points for the liquid phase and for phase boundaries. Both the liquid phase and (Pb) were described by the Redlich-Kister model. The calculated eutectic temperature and composition, as well as the solubility of Cd in (Pb), are very close to the literature information, as are the thermodynamic functions of the liquid phase. The effect of pressure on the melting curves of both Cd and Pb and on the eutectic temperature and composition were considered.

Thermodynamic Study of Liquid Mg-In-Sn Alloys

Liquid Mg-In-Sn alloys were studied by the emf method using concentration cells with liquid electrolyte. Experiments were performed for 30 alloys along three sections on the Gibbs triangle with constantt = 0.25, 0.50, 0.75 [t = XSn/(XSn + XIn)] and for magnesium concentration from 0.1 to 0.65 at temperatures from 950 to 1100 K. From the change of the slope of the emf versusT, points on the liquidus surface for sixteen alloys were detected. Calculated partial excess Gibbs energies δGexMg and partial enthalpies δHMg were compared with the results of previous work.