Larry Kaufman

Coupled phase diagrams and thermochemical data for transition metal binary systems-VI☆

Abstract A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher order systems. The current paper, which is part of a series, details the following twelve binary systems: silicon-carbon, aluminum-silicon, titanium-silicon, chromium-silicon, manganese-silicon, iron-silicon, cobalt-silicon, nickel-silicon, copper-silicon, niobium-silicon, molybdenum-silicon and tungstensilicon. This brings the total of such systems covered to date to sixty-nine. This paper together with past and projected contributions will cover other binary members in order to permit computation of a wide range of ternary and higher order systems.

Thermodynamic assessment of the Cu-Ti-Zr system

Abstract Equilibrium phase relations in the Cu–Ti–Zr system are calculated using the Calphad approach. Thermodynamic model parameters for the Ti–Zr, Cu–Ti and Cu–Zr systems, previously obtained in the literature, are used. New thermodynamic descriptions for the ternary interaction parameters of the liquid are obtained from experimental information. Additionally, the Gibbs energy of formation for the ternary phase Cu 2 TiZr phase is also assessed from experimental data. A new description of the CuTi 2 and CuZr 2 phases, treated as single phases, is developed. The parameters obtained in this assessment are later used for the calculation of selected isothermal sections and the projected liquidus surface of this system over the entire composition range. This model allows the prediction of a series of invariant points involving the liquid phase, at lower temperatures than neighboring binary eutectics.

Phase transformations in iron-ruthenium alloys under high pressure☆

Abstract At atmospheric pressure, iron-ruthenium alloys containing less than 12 atom percent ruthenium exhibit a diffusionless α(b.c.c.) ⇄ γ(f.c.c.) transformation on heating and cooling, while alloys containing 12–36 atom percent ruthenium exhibit a diffusionless ϵ(h.c.p.) ⇄ γ(f.c.c.) transformation. High pressure displaces the α → γ reaction to lower temperatures, but shifts the ϵ ⇄ γ reaction to higher temperatures. These effects appear to be governed by the pressure dependence of the thermodynamic properties. The application of pressure also produces a new transformation, α ⇄ ϵ, at room temperature in alloys which contain the α-phase at atmospheric pressure. Pressure-temperature diagrams at constant composition thus contain triple points involving α(b.c.c.), γ(f.c.c.) and ϵ(h.c.p.). As the ruthenium content is increased, the triple-point pressure decreases significantly. Comparison of the alloy pressure-temperature diagrams with the high-pressure behavior of iron demonstrates that the pure metal also exhibits a triple point, at which the high-pressure, low-temperature phase is ϵ. A thermodynamic analysis has yielded values of ΔFα → ϵ[T] for pure iron, thus establishing the relative stability of the ϵ-phase in iron.

Coupled pair potential, thermochemical and phase diagram data for transition metal binary systems-VII☆☆☆

Abstract A data base covering the transition metals has been developed which permits coupling of thermochemical and phase diagram data and can readily be employed to compute ternary and higher order systems. The current paper, which is part of a series extends the elements covered by this data base to boron bringing the total of elements to fourteen and the total of binary systems to ninety one. The current study also incorporates the pair potential method for calculation of the heat of formation of fcc and bcc phases into the analysis providing a means for incorporating model calculation of thermochemical data into the general analysis.

Calculation of ternary systems containing III-V and II-VI compound phases

Abstract A data base covering the binary systems composed of Aluminum, Gallium, Indium, Phosphorus, Arsenic and Antimony has been constructed by analyzing the fifteen combinations of these elements in terms of lattice stability, solution phase and compound parameters. Partial isothermal sections in the P-In-As, As-In-Sb, P-Ga-As, Ga-Sb-In and Al-Sb-Ga systems were then calculated using the foregoing data base for comparison with experimental isothermal sections and quasi-binary III-V phase diagrams. It was found that ternary liquid and III-V compound interaction parameters were required to attain good agreement in some cases. Similar calculations were performed for the Te-Cd, Hg-Cd and Te-Hg binary systems and the Cd-Te-Hg ternary systems at pressures up to 74 atmospheres. Comparison of the calculated results with experimental data on tie-line compositions between Cd-Te-Hg liquid and quasi-binary CdTe-HgTe alloys is important in the liquid phase epitaxial growth of controlled band gap electro-optical materials.

The Martensitic Transformation in the Iron-Nickel System

The martensite-start temperature (Ms) on cooling and the austenite-start temperature (As) on heating in the iron-nickel system have been determined between 9.5 and 33.2 atomic pet nickel. By considering the α and ψ phases to be regular solid solutions, it is shown that To, the temperature at which δFα→ψ = 0, lies approximately halfway between Ms and As. This relationship has been corroborated by a study of the effect of plastic deformation on Ms and As.

Calculation of quasibinary and quasiternary oxide systems — I

Abstract A data base is being developed for calculation of quasi-binary and quasi-ternary phase diagrams of ceramic systems (1–3). Previous segments of this base cover combinations of Cr2O3, MgO, Al2O3, Fe2O3, Fe3O4, “FeO”, SiO2, CaO, Si3N4 and AlN. Lattice Stability, Solution and Compound Phase Parameters were derived covering the liquid, spinel, corundum, periclase, crystobalite, tridymite, quartz, hexagonal and beta prime phases which appear in the binary systems composed of pairs of these compounds. Compound phases formed from specific binary combinations of these compounds (i.e. MgO·Cr203) were also characterized. This description is based on observed thermochemistry and phase diagrams for the binary systems of interest. Selected ternary systems have been computed based on the foregoing data base for comparison with experimental sections in order to illustrate the usefulness of the data base. The present paper extends the data base to cover BeO, Y2O3 and Ce2O3 additions. Moreover, ternary sections in the SiO2-MgO-Si3N4, SiO2-Y2O3-Si3N4 and SiO2-Ce2-O3-Si3N4 were calculated between 1900K and 2100K for comparison with experiment.

Thermodynamic modeling of the ZrO 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 ZrO2−x,β ZrO2−x and α ZrO2−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.

Thermodynamic properties of h.c.p. iron and iron-ruthenium alloys

Abstract Specific heat measurements on a series of hexagonal close packed iron-ruthenium alloys have been performed between 60°K and 300°K. Measurements of the vapor pressure of iron over f.c.c. and h.c.p. iron-ruthenium alloys have been performed at 1600°K. The results have been employed to describe the lattice stability of h.c.p. iron and the thermodynamic properties of the iron-ruthenium system for comparison with earlier results estimated on the basis of high pressure and martensitic transformation data. In support of the theoretical conclusions deduced earlier, and in contrast to present views, the vibrational entropy of h.c.p. iron exceeds that of the b.c.c. form of iron.

Calculation of quasi binary and quasiternary oxynitride systems — III

Abstract A data base is being developed for calculation of quasi-binary and quasi-ternary phase diagrams of ceramic systems. Initially the base was restricted to the following oxides: Cr2O3, MgO, Fe2O3, Fe3O4, FeO, Al2O3, CaO and SiO2. Lattice Stability, Solution and Compound Phase Parameters were derived covering the liquid, spinel, corundum, periclase, crystobalite, tridymite and quartz phases which appear in the binary systems composed of these oxides. These parameters were selected in accordance with the observed thermochemical properties and phase diagrams of these binary systems. The usefulness of this analytical description was illustrated by computing isothermal sections for ternary systems composed of these oxides. The above mentioned data base has now been expanded to cover combinations of the oxides with silicon nitride, Si3N4, and aluminum nitride, A1N thus permitting computation of oxynitride SIALON ceramic systems which are of current practical interest. The current analysis provides isothermal sections in the Si3N4-Al2O3-A1N and SiO2-A12O3-Si3N4 systmes as well as computed values for the free energy of formation of the beta sialons in the Si3N4-A12O3-A1N system and the X phase in the SiO2-Al2O3-Si3N4 system. The former results are compared with independent calculations reported by Doerner et.al. at CALPHAD VIII and published in the current issue of the CALPHAD Journal.