Thermodynamic assessment of the Cu-In binary system

On the basis of thermodynamic properties and phase diagram data, the Cu-In binary system was thermodynamically assessed. The phases in this system were modeled using the Redlich-Kister expression for the Gibbs energies of the solution phases, adopting three-sublattice models for γ and η′, and assuming stoichiometric compounds for other intermetallic phases. Then a set of consistent parameters was obtained by the CALPHAD method, by which reasonable agreement can be realized between the thermodynamic properties for various phases and phase relations of this system.     

Thermodynamic assessment of the Cu-In binary system

On the basis of thermodynamic properties and phase diagram data, the Cu-In binary system was thermodynamically assessed. The phases in this system were modeled using the Redlich-Kister expression for the Gibbs energies of the solution phases, adopting three-sublattice models for γ and η′, and assuming stoichiometric compounds for other intermetallic phases. Then a set of consistent parameters was obtained by the CALPHAD method, by which reasonable agreement can be realized between the thermodynamic properties for various phases and phase relations of this system.     

Thermodynamic assessment of the Hg-Sn system

A thermodynamic assessment of the Hg-Sn system has been carried out using the CALPHAD method. The comprehensive assessment covers the extensive phase diagram data as well as the enthalpy, activity, and vapor pressure data. Two cases of intermetallic compounds in the Hg-Sn system are considered. Case 1 considers the intermetallic compounds β, γ, and HgSn₄ as having no solubility and can thus be treated as the stoichiometric phases β-HgSn₃₈, γ-HgSn₁₂, and HgSn₄. Case 2 uses a sublattice model to more accurately describe a solubility of the γ phase; it also considers the stoichiometric δ-HgSn₇ phase. The ε phase was considered to be metastable and neglected in the thermodynamic assessment. Thermodynamic parameters have been optimized using all the assessed experimental thermodynamic and phase equilibrium data. Both calculated phase diagrams of the Hg-Sn system (Cases 1 and 2) and the thermodynamic data are reasonable and satisfactory when compared with literature data. Future crucial experiments are suggested.     

Thermodynamic assessment of the Hg-Sn system

A thermodynamic assessment of the Hg-Sn system has been carried out using the CALPHAD method. The comprehensive assessment covers the extensive phase diagram data as well as the enthalpy, activity, and vapor pressure data. Two cases of intermetallic compounds in the Hg-Sn system are considered. Case 1 considers the intermetallic compounds β, γ, and HgSn₄ as having no solubility and can thus be treated as the stoichiometric phases β-HgSn₃₈, γ-HgSn₁₂, and HgSn₄. Case 2 uses a sublattice model to more accurately describe a solubility of the γ phase; it also considers the stoichiometric δ-HgSn₇ phase. The ε phase was considered to be metastable and neglected in the thermodynamic assessment. Thermodynamic parameters have been optimized using all the assessed experimental thermodynamic and phase equilibrium data. Both calculated phase diagrams of the Hg-Sn system (Cases 1 and 2) and the thermodynamic data are reasonable and satisfactory when compared with literature data. Future crucial experiments are suggested.     

Growth of intermetallic phases in Al/Cu composites at various annealing temperatures during the ARB process

The purpose of this study is to discuss the effect of annealing temperatures on growth of intermetallic phases in Al/Cu composites during the accumulative roll bonding (ARB) process. Pure Al (AA1100) and pure Cu (C11000) were stacked into layered structures at 8 cycles as annealed at 300 °C and 400 °C using the ARB technique. Microstructural results indicate that the necking of layered structures occur after 300 °C annealing. Intermetallic phases grow and form a smashed morphology of Al and Cu when annealed at 400 °C. From the XRD and EDS analysis results, the intermetallic phases of Al₂Cu (θ) and Al₄Cu₉ (γ₂) formed over 6 cycles and the AlCu (η₂) precipitated at 8 cycles after 300 °C annealing. Three phases (Al₂Cu (θ), Al₄Cu₉ (γ₂), and AlCu (η₂)) were formed over 2 cycles after 400 °C annealing.     

Thermodynamic assessment of the Fe-U binary system

The Fe-U system is one of the binaries of the U-Fe-Zr-O quaternary system that is important for a safe nuclear program. A new thermodynamic assessment of Fe-U is presented, taking into account some recent thermodynamic measurements: enthalpy of formation and of melting as well as heat capacities for both intermetallic compounds Fe₂U and FeU₆. The calculated phase diagram and thermodynamic data generally agree very well with the experimental values. The calculated temperature of the peritectic transformation [FeU₆ ↔ liquid + bcc-U] is equal to 1104 K, which is higher than in the previous assessments, but in agreement with Labroche’s value. However, the experimental melting enthalpy of FeU₆ is not reproduced by the present set of thermodynamic parameters.     

Thermodynamic assessment of the Fe-U binary system

The Fe-U system is one of the binaries of the U-Fe-Zr-O quaternary system that is important for a safe nuclear program. A new thermodynamic assessment of Fe-U is presented, taking into account some recent thermodynamic measurements: enthalpy of formation and of melting as well as heat capacities for both intermetallic compounds Fe₂U and FeU₆. The calculated phase diagram and thermodynamic data generally agree very well with the experimental values. The calculated temperature of the peritectic transformation [FeU₆ ↔ liquid + bcc-U] is equal to 1104 K, which is higher than in the previous assessments, but in agreement with Labroche’s value. However, the experimental melting enthalpy of FeU₆ is not reproduced by the present set of thermodynamic parameters.     

Experimental Investigation and Thermodynamic Description of the Cu-Zr System

The Cu-Zr binary system is re-investigated via experiment and thermodynamic modeling. Four alloys were prepared by arc melting in order to check the controversial phase equilibria reported in the literature. Both as-cast and annealed alloys were examined by optical microscopy, x-ray diffraction and electron probe microanalysis, and the phase transformation temperatures were measured by differential scanning calorimetry. The intermetallic compounds, Cu₂₄Zr₁₃, Cu₂Zr and Cu₅Zr₈, were demonstrated to be not the stable phases. Based on the literature information and present experimental data, the Cu-Zr system was critically evaluated by means of CALculation of PHAse Diagram approach. A set of self-consistent thermodynamic parameters was obtained, and the calculated phase diagram and thermodynamic properties are in a satisfactory agreement with the experimental data.     

Phase equilibria of the cu-in system I: Experimental investigation

Portions of the Cu-In phase diagram were redetermined experimentally, specifically in the compositional region from 32.0 to 100 at % In. The experimental techniques used were differential scanning calorimetry (DSC), differential thermal analysis (DTA), powder X-ray diffraction (XRD), and electron probe microanalysis (EPMA). The results indicate that the phase Cu₁₁ln₉ is stable to low temperatures rather than decomposing at 157 °C. The existence of the“phase bundle” at compositions ranging from 32 to 38 at.% In was not supported by our experimental data. Only two phases were found to exist: η at temperatures higher than 305 to 389 °C, and η at lower temperatures. Minor phase boundary adjustments were made in this region. The peritectic temperature for the formation of Cu₁₁ln₉ was found to be 307 ± 1 °C, and the L = Cu₁₁ln₉ + (In) eutectic temperature was found to be 154 ± 1 °C. In the study to determine the temperature stability of Cu₁₁lns₉, it was found that Culm exists at low temperatures, but the stability was not investigated.     

Phase equilibria in the cobalt oxide-copper oxide system

Thermodynamic properties were determined for the system cobalt oxide-copper oxide by means of an electromotive force (EMF) measurement techniques using galvanic cells with calciastabilized zirconia (CSZ) as the solid electrolyte and with air as the reference electrode according to the following schemes: CuO, Cu₂O | CSZ | air and CoO-CuO, Cu₂O CSZ | air for composition variables y=X_Cu/(X_Co+X_cu equal to 0.05, 0.15, 0.25, 0.35, 0.45, 0.667, and 0.8; and within the temperature interval 1200–1350 K. Thermodynamic properties calculated directly from EMF values were combined with the available literature data on phase equilibria, and thermodynamic properties of solid phases in the Co-Cu-O system were assessed. Both terminal solid solutions, (Co,Cu)O and (Cu,Co)O, were described by a sublattice model with Redlich-Kister excess term. The interaction parameters for both (Co,Cu)O and (Cu,Co)O solid solutions and the Gibbs energy of formation for the intermediate phase Cu₂CoO₃ were obtained. The Gibbs energies of fictive end-members: monoclinic “CoO” and “CuO” with rock salt structure were derived as well. The phase diagrams were calculated using the assessed thermodynamic parameters. The (T, y) phase diagram was calculated for existence under ambient air. The property diagrams log₁₀P(O₂) versus composition and activity of CuO versus composition were calculated at 1273 K. The results of our calculations were in a good agreement with available experimental data. This paper was presented at CALPHAD XXX International Conference on Phase Diagram Calculations in York, UK, May 27–June 1, 2001, and appeared in the Conference Abstracts on Page 75.     

Growth of η phase scallops and whiskers in liquid tin-solid copper reaction couples

In the microelectronics industry, many solder junctions rely upon reaction between a copper substrate and a molten tin-based alloy. For the tin/copper system, interfacial continuity is afforded by the formation of the η (Cu₆Sn₅) and ɛ (Cu₃Sn) phase intermetallic compounds. The η grows in a scalloped morphology along the tin interface with whiskers emanating from their tops. This article quantitatively describes the unusual growth behavior of the η phase scallops and whiskers formed during reaction of liquid tin with a solid copper substrate. For more information, contact R. Gagliano, Northwestern University, Department of Materials Science, 2225 N. Campus Drive, Evanston, Illinois 60208; e-mail r-gagliano@northwestern.edu.     

Phase equilibria in the cobalt oxide-copper oxide system

Thermodynamic properties were determined for the system cobalt oxide-copper oxide by means of an electromotive force (EMF) measurement techniques using galvanic cells with calciastabilized zirconia (CSZ) as the solid electrolyte and with air as the reference electrode according to the following schemes: CuO, Cu₂O | CSZ | air and CoO-CuO, Cu₂O CSZ | air for composition variables y=X_Cu/(X_Co+X_cu equal to 0.05, 0.15, 0.25, 0.35, 0.45, 0.667, and 0.8; and within the temperature interval 1200–1350 K. Thermodynamic properties calculated directly from EMF values were combined with the available literature data on phase equilibria, and thermodynamic properties of solid phases in the Co-Cu-O system were assessed. Both terminal solid solutions, (Co,Cu)O and (Cu,Co)O, were described by a sublattice model with Redlich-Kister excess term. The interaction parameters for both (Co,Cu)O and (Cu,Co)O solid solutions and the Gibbs energy of formation for the intermediate phase Cu₂CoO₃ were obtained. The Gibbs energies of fictive end-members: monoclinic “CoO” and “CuO” with rock salt structure were derived as well. The phase diagrams were calculated using the assessed thermodynamic parameters. The (T, y) phase diagram was calculated for existence under ambient air. The property diagrams log₁₀P(O₂) versus composition and activity of CuO versus composition were calculated at 1273 K. The results of our calculations were in a good agreement with available experimental data.     

Thermodynamic optimization of the Co-Zn system

Literature information and authors’ experimental data have been used for the evaluation of optimized polynomial coefficients serving to calculate the cobalt (Co)-zinc (Zn) phase diagram. The programs BINGSS and THERMO-CALC have been used for the optimization. The binary liquid phase, the solid Co-based face-centered-cubic (fcc) and hexagonal close-packed solutions, as well as the intermediate β-, β₁-, and γ-compounds have been treated as disordered substitutional phases. The phases with narrow homogeneity ranges (δ, γ₁, and γ₂) have been modeled as stoichimetric Co₂Zn₁₅, CoZn₇, and CoZn₁₅, respectively. The calculated phase diagram and thermodynamic quantities are in agreement with the experimental data. For the first time, a eutectoid decomposition (at around 658 K) of the fcc solutions has been predicted. Moreover, the calculations have shown the possibility for a magnetically induced miscibility gap involving both forms (paramagnetic and ferromagnetic) of the fcc solutions.     

Determination of liquid-phase boundaries in Zn-Fe-Mx systems

Iron solubilities in molten Zn-Al alloys were experimentally determined at temperatures from 450 to 480 °C, a range relevant to continuous galvanizing operation. The Fe solubility was found to decrease slowly with increasing Al content in regions where ζ (FeZn₁₃) or δ (FeZn₇) is the equilibrium compound and rapidly in the region where the η (Fe₂Al₅Zn _x ) phase is the equilibrium compound. Analyses of the experimental data indicated that Fe solubility is governed by the thermodynamic properties of the intermetallic compound in equilibrium with the molten Zn-Al alloy. A model was developed to describe the liquid surface in the Zn-rich corner of the Zn-Fe-Al system. The methodology developed in the exercise has proven applicable for the determination of the liquid surface in the Zn-Fe-Ni system.     

The ternary Gd-Li-Mg system: Phase diagram study and computational evaluation

The binary Gd-Li and the ternary Gd-Li-Mg systems were studied experimentally by thermal analysis and phase equilibration and also by thermodynamic calculations using the CALPHAD method. Ternary phase equilibria at 250 °C were studied with 55 different alloys that were annealed for 400 h and analyzed by x-ray diffractometry. A thermodynamic assessment of the binary Gd-Li system was also performed and the calculated phase diagram is presented. In the Gd-Li-Mg system, ternary solubilities of Li in GdMg (up to 5 at.% Li), GdMg₂ (up to approximately 3 at.% Li), and GdMg₃ (up to 5 at.% Li) were found at 250 °C. No ternary compound was observed. Lattice parameters for different compositions are given for these phases. Thermal analysis using a ternary key sample of composition near the invariant reaction L′=L+(βGd)+GdMg provided the data that were needed to determine a thermodynamic parameter for the ternary liquid. Thermodynamic data sets for the ternary solid solution phases were also developed. Based on the present data sets and those of the binary Gd-Mg and Li-Mg systems from the literature, the phase equilibria in the entire ternary system were calculated. Isothermal and vertical sections of the phase diagram and the projection of the liquidus surface are shown. These calculated phase diagrams are well supported by the experimental data.     

The ternary Gd-Li-Mg system: Phase diagram study and computational evaluation

The binary Gd-Li and the ternary Gd-Li-Mg systems were studied experimentally by thermal analysis and phase equilibration and also by thermodynamic calculations using the CALPHAD method. Ternary phase equilibria at 250 °C were studied with 55 different alloys that were annealed for 400 h and analyzed by x-ray diffractometry. A thermodynamic assessment of the binary Gd-Li system was also performed and the calculated phase diagram is presented. In the Gd-Li-Mg system, ternary solubilities of Li in GdMg (up to 5 at.% Li), GdMg₂ (up to approximately 3 at.% Li), and GdMg₃ (up to 5 at.% Li) were found at 250 °C. No ternary compound was observed. Lattice parameters for different compositions are given for these phases. Thermal analysis using a ternary key sample of composition near the invariant reaction L′=L+(βGd)+GdMg provided the data that were needed to determine a thermodynamic parameter for the ternary liquid. Thermodynamic data sets for the ternary solid solution phases were also developed. Based on the present data sets and those of the binary Gd-Mg and Li-Mg systems from the literature, the phase equilibria in the entire ternary system were calculated. Isothermal and vertical sections of the phase diagram and the projection of the liquidus surface are shown. These calculated phase diagrams are well supported by the experimental data.     

Determination of liquid-phase boundaries in Zn-Fe-Mx systems

Iron solubilities in molten Zn-Al alloys were experimentally determined at temperatures from 450 to 480 °C, a range relevant to continuous galvanizing operation. The Fe solubility was found to decrease slowly with increasing Al content in regions where ζ (FeZn₁₃) or δ (FeZn₇) is the equilibrium compound and rapidly in the region where the η (Fe₂Al₅Zn _x ) phase is the equilibrium compound. Analyses of the experimental data indicated that Fe solubility is governed by the thermodynamic properties of the intermetallic compound in equilibrium with the molten Zn-Al alloy. A model was developed to describe the liquid surface in the Zn-rich corner of the Zn-Fe-Al system. The methodology developed in the exercise has proven applicable for the determination of the liquid surface in the Zn-Fe-Ni system.     

Thermodynamic reassessment of the Cu-O phase diagram

Parts of the copper-oxygen equilibrium phase diagram were reassessed using the calculation of phase diagram technique (CALPHAD). The model parameters were optimized to yield the best fit between calculated and experimentally determined phase equilibria at elevated oxygen pressures up to 11 MPa. The Cu-O liquid phase is represented by the two-sublattice model for ionic liquids containing copper on the cation sublattice with formal valences of Cu⁺¹, Cu⁺², and Cu⁺³. The presence of Cu⁺³ ions in the liquid phase, corresponding to a formation of Cu₂O₃ species, was the key assumption of this model. Congruent melting of CuO at 1551 K under an oxygen pressure of ∼126.8 MPa is predicted, which is considerably below previous theoretical values.