Thermodynamic assessment of Co-Cr-W ternary system

The Co-Cr-W ternary system was critically assessed using the CALPHAD technique.The solution phases including the liquid,γ-Co,ε-Co and α-Cr were described by a substitutional solution model.The σ,μ and R phases were described by three-sublattice models of（Co,W）8（Cr,W）4（Co,Cr,W）18,（Co,Cr,W）7W2（Co,Cr,W）4 and（Co,W）27（Cr,W）14（Co,Cr,W）12,respectively,in order to reproduce their homogeneity ranges.A self-consistent set of thermodynamic parameters for each phase was derived.The calculated isothermal sections at 1 000,1 200 and 1 350 ℃ are in good agreement with the experimental data.A eutectoid reaction of R μ＋γ-Co＋σ in this ternary system was predicted to occur at 1 022 ℃.

Thermodynamic re-assessment of Fe-Ti binary system

The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.

Thermodynamic assessment of Au-Pt system

The thermodynamic re-assessment of Au-Pt binary system was carried out by using the Calphad method and based on the recent experimental data. The Gibbs energies of face-centred cubic and liquid phases were described by a sub-regular solution model with the Redlich-Kister equation. Much effort was taken to reproduce the phase equilibrium results and thermodynamic properties of the solid phase, including the activity and mixing enthalpy. The constraint of the third law of thermodynamics was also considered in the assessment. According to the presently assessed results, the miscibility gap region in the Au-Pt system slightly shifts to the Au-rich side, and the critical !0oint of the miscibility gap is about 1200 ℃ and Au-56% Pt.

Thermodynamic assessment of Ni-Yb binary system

On the basis of the experimental data of phase equilibria and thermochemical properties available from literatures, a critical assessment for the Ni?Yb binary system was carried out using the CALPHAD (calculation of phase diagrams) method. The liquid phase is modeled as the associate model with the constituent species Ni, Yb and YbNi3, owing to the sharp change of the enthalpy of mixing of liquid phase at the composition of around 25% Yb (mole fraction). The terminal solid solutions FCC_A1 (Ni/Yb) and BCC_A2 (Yb) are described by the substitutional solution model with the Redlich?Kister polynomial. The intermetallic compounds, Yb2Ni17, YbNi5, YbNi3, YbNi2, α-YbNi and β-YbNi, are treated as strict stoichiometric compounds, since there are no noticeable homogeneity ranges reported for these compounds. A set of self-consistent thermodynamic parameters for the Ni?Yb binary system are obtained. According to the presently assessed results, the thermochemical properties and the phase boundary data can be well reproduced.

Thermodynamic assessment of ZnO-SiO_2 system

ZnO-containing slags are common in pyrometallurgical processing of the base metals and steel.This caused the interest to the thermodynamics of the ZnO-SiO2 system.A complete literature survey,critical evaluation of the available experimental data and a thermodynamic optimization of the phase equilibria and thermodynamic properties of the system ZnO-SiO2 at 1.013×105 Pa are presented.The molten oxide was described as an associate solution.The properties of liquid were reassessed and enthalpy term of the Gibbs energy of solid Zn2SiO4 was re-fitted to be compatible with the new data in the willemite primary phase field.The thermodynamic data set agrees well with the recent experimental observations.It can be used for predicting,e.g.,the thermodynamic properties and the domains of the phase diagram,like critical point of the liquid miscibility gap,with a better accuracy than using the previous assessments.A set of optimized model parameters were obtained,reproducing the reliable thermodynamic and phase equilibrium data within their experimental errors from 298 K to liquidus temperatures,over the entire composition range.The created database can be used in a Gibbs energy minimization software to calculate the thermodynamic properties and the phase diagram sections of interest.

Thermodynamic assessment of the Ni-Sb binary system

The Ni-Sb binary alloy system was thermodynamically assessed using CALPHAD approach in this article. Excess Gibbs energies of solution phases, liquid and fcc phases, were formulated using the Redlich-Kister expression. The intermediate phases were modeled by the sublattice model with （Ni,Va）0.5（Ni,Sb）0.25（Ni）0.25 for Ni3Sb_HT phase and （Ni,Va）0.3333（Sb）0.3333（Ni,Va）0.3333 for NiSb phase. The other phases including Ni3Sb, Ni7Sb3, and NiSb2 were treated as stoichiometric compound owing to their narrow composition ranges. Based on the reported thermodynamic properties and phase diagram data, the thermodynamic parameters of these phases were optimized, and the obtained values can reproduce the available experimental data well.

Thermodynamic Assessment of Interaction Relation between Lanthanum and Constituent Elements in Sn-Pb Alloy

The interaction relation between lanthanum and the constituent elements of Sn-Pb alloy system was analyzed by using the thermodynamic models including Miedema formation energy model for binary system, Tanaka modification by excess entropy and the Chou geometric model for ternary system. The thermodynamic calculaton results show that lanthanum has higher affinity for Sn in the Sn-Pb system. This is an important foundation for the improvement of the metallurgical properties of Sn-Pb solder alloy by adding rare earth elements.

THERMODYNAMIC ASSESSMENT OF THE ZrO_2-AIO_(1.5) SYSTEM

The ZrO2-AIO1.5 quasibinary system has been assessed by means of the CALPHAD (CALculation of PHAse Diagram) technique. The liquid phase, cubic (fluorite-type) zirconia solid solution and tetragonal zirconia solid solution are described by a regular solution model. The monoclinic zirconia and a-AIO1.5 are treated as stoichiometric phase. A consistent set of optimized parameters describing the system have been obtained to agree with almost all of the available experimental data. Comparisons between the assessed and experimental data are presented. It is shown that further studies are needed for equilibrium solubilities of AIO1.5 in ZrO2 phases.

A thermodynamic assessment of Ce-Al system

The optimized descriptions of the phase diagram and thermodynamic properties for Ce-Al system have been obtained from experimental thermodynamic and phase diagram data by means of the computer program THERMO-CALC based on the least squares method, using models for the Gibbs energy of individual phases. The system contains five intermetallic compounds. The calculated standard enthalpies of Ce_3Al, CeAl, CeAl_2, CeAl_3 and Ce_3Al_ 11 are -26.7, -48.9, -48.4, -44.0 and -41.7 kJ/mol, respectively. A consistent set of thermodynamic parameters was derived. The optimized and experimental data are in good agreement.

Thermodynamic Assessment of Fe-Dy System

The phase diagram and thermodynamic data of the FeDy system were critically assessed by means of the computer programs THERMOCALC, using models for the Gibbs energies of individual phases. The system contains four intermetallic compounds. Good agreement is obtained between the calculation and experimental results.

Thermodynamic Assessment of the ZrO_2-CeO_2 and ZrO_2-CeO_(1.5) Binary System

An optimal set of thermodynamic parameters of the ZrO2-CeO1.5 system has been obtained using phase diagram data by modern CALPHAD (CALculation of PHAse Diagrams) technique. The liquid and other solid solution phases were regarded as substitutional solution. The ordered Zr2Ce2O7 phase was treated as a stoichiometric compound. The ZrO2-CeO2 system has been re-optimized with new reference state. A comparison between the ZrO2-CeO2 system and ZrO2-CeO1.5 system has been made through calculation. With the calculation, the experimental information is well reproduced and a good agreement is obtained.

Thermodynamic assessment of Mg-Ni-Y system focusing on long-period stacking ordered phases in the Mg-rich corner

The long-period stacking ordered phases(LPSOs) in Mg-Ni-Y system have been attracting great interest as effective strengthening components because of their unique structural characteristics and deformation mechanism.However,the phase relationships in LPSOs are complicated and unclear,which restricts the design of advanced magnesium-based alloys.The aim of the present work is to experimentally determine the phase equilibria relationships focusing on LPSOs and establish the thermodynamic description for Mg-Ni-Y system.Four types of LPSOs,that is,14H,12R,18R and 10H,are confirmed through equilibrated alloys and high-resolution transmission electron microscopy(HR-TEM).The formation enthalpies of LPSOs(14H,12R,18R and 10H) are calculated based on density functional theories(DFT) calculations.A new ternary compound,termed as τ phase,is observed for the first time which is likely to be the distorted structure of 12R as determined from the TEM image which shows a 12-layer closed packing plane distance of 3.252nm and a shear angle of 83.2°between(0002) and(10■0) planes.Based on the determined phase equilibria relationship,the Mg-Ni-Y system is assessed and a selfconsistent description is obtained where the LPSOs are modeled as the stoichiometric compounds.The comparison between the calculation result and experimental data suggests the accuracy of the present thermodynamic database in the Mg-rich corner.

Thermodynamic reassessment of Ga-Hg and Mg-Hg systems

The Ga-Hg binary system was thermodynamically assessed by the CALPHAD method, but only configuration contributions were considered to the entropy of the liquid. The Mg-Hg binary system has not been assessed yet. In the assessments of the Ga-Hg and Mg-Hg binary systems, solutions including liquid and hcp (Mg) were treated as substitution solutions, of which the excess Gibbs energies were formulated with the Relich-Kister polynomial. The intermetallic phases in the Mg-Hg binary system, Mg3Hg, Mg5Hg2, Mg2Hg, Mg5Hg3, MgHg, and MgHg2, were described as stoichiometric compounds. Based on the reported experimental data and thermodynamic properties of the phase diagram, sets of self-consistent parameters describing all phases in the Ga-Hg and the Mg-Hg binary systems were obtained.

Thermodynamic assessment of Cu-Cd system

A thermodynamic assessment of the Cu-Cd system has been carried out by CALPHAD technique.The liquid phase, FCC_A1(Cu)and HCP_A3(Cd)terminal phases are described by a simple substitutional model,their excess Gibbs energy is formulated with the Redlich-Kister expression.The system contains four intermediate compounds,includingβ(Cu2Cd),γ(Cu4Cd3), δ(Cu5Cd8)andε(Cu3Cd10).Theδphase is described by a two-sublattice model and the other three intermediate phases are treated as stoichiometric phases.The optimization is carried out in the Thermo-Calc package.A set of self-consistent thermodynamic parameters are obtained.The calculated phase diagram and thermodynamic properties agree well with the available experimental data.

Thermodynamic assessment of Mg-Ga binary system

In order to obtain the thermodynamic description of the Mg-Ga binary system,the thermodynamic assessment of the system was carried out using the CALPHAD method through Thermo-calc software package based on the evaluation of all available experimental data from the published literature.The solution phases,including liquid,hcp(Mg) and orthorhombic(Ga),were described by the substitutional solution model,of which the excess Gibbs energies were expressed with the Redlich-Kister polynomial.Meanwhile,all intermetallic compounds,Mg5Ga2,Mg2Ga,MgGa,MgGa2 and Mg2Ga5,were modeled as stoichiometric compounds.A set of self-consistent thermodynamic parameters formulating the Gibbs energies of various phases in the Mg-Ga binary system were obtained finally.The much better agreement is achieved between the calculated results and the reported experimental data.

Thermodynamic Assessment of the Pt-Sb System

The Pt-Sb system was critically assessed by means of CALPHAD technique. Based on the experimental data in the literature, the excess Gibbs energies of the solution phases (liquid, rhombohedral, fcc) were modeled with the Redlich-Kister equation. The five intermetallic compounds, Pt7Sb, Pt3Sb, Pt3Sb2, PtSb, and PtSb2 were treated as stochiometric compounds and expressed as the formula (Pt)m(Sb)n. The intermetallic compound, Pt5Sb with a homogenerity ranges 0.155 -?0.189 Sb, were treated as the formula (Pt,Sb)m(Pt,Sb)n. A set of self-consistent thermodynamic parameters of the Pt-Sb system was obtained.

Thermodynamic Assessment of DyCl_3-MCl (M=Na, K, Rb, Cs) Systems

Using the CALPHAD （Calculation of Phase Diagram） technique, the DyCl3-MCl （M = Na, K, Rb, Cs） systems were optimized and calculated. The modified quasi-chemical model in the pair approximation for short-range ordering was used to describe the Gibbs energies of the liquid phase in these systems. From the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized base on an interactive computer-assisted analysis. The optimized parameters and the experimental data were thermodynamically self-consistent. The optimized results were discussed.

Thermodynamic Assessment of the Scandium-Gold Binary System

The phase diagram and thermodynamic properties of the Sc-Au system were carried out by means of the CALPHAD(calculation of phase diagrams)method through Thermo-Calc software package on the basis of the experimental data of phase equilibria and thermodynamic proprieties from the published literature data.The excess Gibbs energies functions of the solution phases including liquid,face–centered cubic fcc_A1,body-centered hexagonal close–packed hcp_3 and cubic bcc_A2,modeled with Redlich-Kister polynomials functions while all intermetallic compounds have been treated as stoichiometric compounds.The thermodynamic parameters describing various phases in the Sc-Au binary system were finally obtained,and a good agreement is achieved between the calculated results and the reported experimental data.

Thermodynamic Assessment of the Fe-Y System

By means of the software Thermo Calc, the Fe Y system is assessed. It gives the thermodynamic parameters of individual phases, including the solutions bcc, fcc, hcp, liquid and the intermetallic compounds Fe 17 Y 2, Fe 23 Y 6, Fe 3Y and Fe 2Y, which are treated as stoichiometric compounds.

Thermodynamic Assessment of Co-Y System

By means of the Software Thermo-Calculation, the Co-Y system is assessed. It gives the thermody-namic parameters of individual phases, including the solutions bee, fee, hep, liquid and the intermetalliccompounds Co_(17)Y-2, Co_5Y, Co_7Y_2,Co_3Y,Co_2Y, Co_3Y_2,Co_7Y_6,CoY, Co_3Y_4,Co_5Y_8 and CoY-3, whichare treated as stoichiometric compounds. Good agreement is obtained between calculation and experiments.