FeS—PbS和PbS—ZnS二元系的热力学优化

采用Ｒｅｄｌｉｃｈ－Ｋｉｓｔｅｒ多项式描述体系液相的过剩自由焓，根据试验相图和已知的热力学数据优化得到了ＦｅＳ－ＰｂＳ和ＰｂＳ－ＺｎＳ二元素的热力学参数。用优化结果计算的相图与试验测量值吻合较好。     

FeS-PbS和PbS-ZnS二元系的热力学优化

采用ＲｅｄｌｉｃｈＫｉｓｔｅｒ多项式描述体系液相的过剩自由焓,根据试验相图和已知的热力学数据优化得到了ＦｅＳＰｂＳ和ＰｂＳＺｎＳ二元系的热力学参数。用优化结果计算的相图与试验测量值吻合较好。     

Cu-In体系的热力学优化

评估了Cu-In体系的相平衡和热力学实验结果,并对体系进行了热力学优化。采用替代模型描述体系的液相和富铜固溶体相,双亚晶格模型描述线性化合物相,三亚晶格模型描述非线性化合物相,结合选取合理的实验数据,优化得到Cu-In体系各相的热力学参数,用优化结果计算的相图以及热力学性质与实验结果吻合。     

Bi-Te二元体系的热力学优化

在综合评估Bi-Te体系实验数据的基础上,结合第一性原理方法计算的各中间化合物的摩尔形成焓,采用CALPHAD方法优化和计算该二元合金体系的平衡相图。液相采用置换式溶体溶液模型,对于化学计量比中间化合物Bi_7Te_3、Bi_2Te_3以及具有较大固溶度的中间相Bi_2Te、BiTe,分别采用Neumann-Kopp规则以及双亚点阵模型描述其热力学函数。通过优化,得到一组合理自洽的热力学参数,并利用该热力学参数计算相图。计算的相图与文献报道的实验信息吻合较好,计算的863 K下液相Bi的活度以及混合焓也与已有的热化学数据符合良好。     

Zr-Nb-O三元系的热力学优化

综合评估了文献报道的Zr-Nb-O三元系及其子二元系的相图及热力学信息。液相的Gibbs自由能采用离子亚晶格模型描述,固溶体相(α,β)和所有化合物(αZrO2,βZrO2,γZrO2,NbO,NbO2和Nb2O5)的Gibbs自由能都采用双亚晶格模型描述。用CALPHAD(CALculation ofPHAse Diagrams)技术,使用Pandat软件中的PanOptimizer优化模块,对Zr-O二元系进行了热力学优化,计算得到的相图和热力学性质与实验结果相吻合。应用优化的Zr-O二元系模型参数,结合Zr-Nb、Nb-O已有的热力学评估结果,对Zr-Nb-O三元系进行了热力学优化,得到了该体系的一套热力学模型参数。计算了Zr-Nb-O三元系在1273,1473和1773 K温度下的等温截面,与实验数据符合得较好。计算了若干该体系在富Zr区α+ββ的相转变温度,结果和实验测量也能较好地吻合。研究结果对建立多元锆合金热力学数据库,以及指导新型锆基合金材料的成分设计具有重要意义。     

Ti-Cr-V与Ti-Cr-Mo合金阻燃机理热力学分析

根据绝热条件下体系平衡时总自由焓最小和焓恒定原理，计算了不同环境温度下钛合金的绝热燃烧温度。计算结果从热力学的角度揭示了铬、钒、钼等元素阻止合金燃烧蔓延的效应和机理。     

碱金属—铝合金形成焓的热力学计算

本文运用Ｍｉｅｄｅｍａ理论系统地研究了铝与碱金属Ｌｉ，Ｎａ，Ｋ，Ｒｂ，Ｃｓ组成的二元合金系统的液态混合焓和固态金形成焓，计算得到了结果同已有的实验结果和第一原理方法计算得到的结合符合得比较好，从而说明，Ｍｉｅｄｅｍａ理论用于铝与碱金属组成的合金系统的形成焓计算是合适的。     

Ti—C-3Ni—Al体系SHS反应热力学分析

计算Ti-C-3Ni-Al体系的自由能,结合体系DSC分析及产物XRD分析结果,研究体系反应的热力学问题。结果表明：该体系中TiC和Ni3Al标准生成自由焓最小,为最稳定的生成物,且产物纯净。     

碱金属－铝合金形成焓的热力学计算

本文运用Ｍｉｅｄｅｍａｌ理论系统地研究了铝与碱金属Ｌｉ、Ｎａ、Ｋ、Ｒｂ、Ｃｓ组成的二元合金系统的液态混合焓和固态合金形成焓。计算得到的结果同已有的实验结果和第一原理方法计算得到的结果符合得比较好，从而说明，Ｍｉｅｄｅｍａ理论用于铝与减金属组成的合金系统的形成焓计算是合适的。     

Be-Cr二元体系热力学优化

在评估现有文献实验相图数据的基础上,采用Calphad技术优化和计算了Be-Cr二元合金体系平衡相图.液相和端际固溶体相采用替换式溶体溶液模型,化学计量比中间化合物CrBe₂和CrBe₁₂采用Neumann-Kopp规则描述它们的热力学函数.利用优化所得的热力学参数计算相图,结果能很好地解释大部分实验数据.本工作还采用Miedema模型估算了中间化合物CrBe₂和CrBe₁₂的摩尔生成焓,并与热力学计算值比较,所得结果符合良好.     

Thermodynamics of formation of Y-Co alloys

The Gibbs free energies, enthalpies, and entropies of phase formation were determined for nine Y-Co intermediate phases from electromotive force measurements. Solid CaF₂ was employed as the electrolyte, and emf measurements were made over the temperature range 850 K to 1200 K. The data indicate that the Gibbs free energies of formation per mole of Y reactant are nearly constant for the four Y-poor phases. Such behavior is associated with the close structural similarity of these phases. The present experimental Gibbs energy data at 973 K are compared with those of the Th-Fe, Th-Co, Th-Ni, La-Co, La-Ni, and Y-Fe systems. It was observed that the Gibbs free energy of formation can be empirically correlated with the total number of valence electrons in these alloy systems. The enthalpy of formation of an equiatomic Y-Co alloy was determined to be −27.1 kJ/mole atoms. This experimental value is in good accord with the theoretical predictions of the Miedema and Watson-Bennett models.     

Thermodynamic assessment of the CaO-MgO-SiO2 system

The phase equilibrium and thermodynamic information of the CaO-MgO-SiO₂ system at 1 atm was reviewed and assessed by using thermodynamic models for the Gibbs energy of all the phases. The assessment was based on recent assessments of the CaO-MgO, CaO-SiO₂, and MgO-SiO₂ systems. Two thermodynamic models were used: the two-sublattice model for ionic liquids for the liquid phase, and the compound energy model for the solid solution phases. The model parameters were evaluated by fitting to the selected experimental data by means of a computer program, which can accommodate a variety of experimental data. A consistent set of parameters was obtained that sat-isfactorily described most of the experimental information. The models were found to be well-suited for the present system, and only a small number of adjustable parameters were needed. Extensive comparisons were made between the calculations and experimental data. Formerly Research Associate, Royal Institute of Technology     

Experimental Study and Thermodynamic Optimization of the FeO-V_2O_3 System

Optimization of the phase diagram of FeO-V2O3 system is a part of an on-going research project to develop a self-consistent multi-component thermodynamic database for vanadium slag from hot metal.Due to the lack of experimental data for optimization,a novel experimental investigation has been carried out by thermal analysis(DSC)with a series of slags on different V2O3 contents(i.e.3mass%-12mass%).All available thermodynamic and phase diagram data for the binary systems have been simultaneously optimized with CALPHAD(Calculation of Phase Diagrams)methods to give one set of model equations for the Gibbs free energy of the liquid slag as functions of composition and temperature.The modified quasi-chemical model was used to describe the binary slag system.It was demonstrated that the calculated phase diagram with the optimized parameters was in good agreement with the experimental data.     

Magnetic contributions to the thermodynamic functions of alloys and the phase equilibria of Fe-Ni system below 1200 K

A generalized approach is proposed to calculate the magnetic contribution to the thermodynamic functions of alloys. This approach is applied successfully to the Fe-Ni binary system. The predicted magnetic specific heat of the fcc phase at 75 at. Pct Ni is in agreement with the experimental data within the accuracies of the data and the predicted values. The magnetic contributions to the Gibbs energies of the fcc and bcc phases for the Fe-Ni alloys obtained from this approach are added to the nonmagnetic portion of the Gibbs energies. The nonmagnetic portion of the Gibbs energy of the fcc phase is obtained from extensive thermochemical data at high temperatures as discussed in the paper immediately following this one. The total Gibbs energies of the fcc, bcc, and the orderedγ′-(FeNi₃) phases are then used to calculate/predict phase equilibria of the Fe-Ni binary at temperatures lower than 1200 K. The calculated equilibria are in agreement with available experimental data. In addition, a irascibility gap of the fcc phase at low temperatures is predicted, resulting in the formation of a monotectoid equilibrium at 662 K as given below: {fx1361-02} The existence of the miscibility gap is due to the magnetic Gibbs energy term of the fcc phase which is composition dependent. Experimental results reported in the literature support the predicted miscibility gap.     

A mathematical model for the solute drag effect on recrystallization

The model for the solute drag effect in phase transformations has been applied to recrystallization, i.e., moving grain boundaries. In this model, the total driving force is dissipated by the interfacial energy, the finite interfacial mobility, the solute drag in boundaries, and diffusion in the matrix ahead of the interface, of which all are taken into account consistently. The effects of the Gibbs energy of segregation and the diffusivity of impurity atoms in boundaries were investigated. The results show that the Gibbs energy of segregation mainly affects the critical composition at which the drastic change in the boundary velocity appears, and the diffusivity of impurity atoms in boundaries mainly affects the velocity reduced by the solute drag effect. In other words, the Gibbs energy of segregation and the diffusivity of impurity atoms in boundaries can be evaluated from experimental data by means of the present model. This model was applied to the Al-Mg system, and the Gibbs energy of segregation and the diffusivity of Mg in boundaries were evaluated from experimental data. The evaluated Gibbs energy of segregation agrees with the estimate based on elastic energy considerations. The diffusivity estimated from this model is smaller than that measured along the grain boundary.     

An experimental study and a thermodynamic evaluation of the Fe-Cr-Mo system

An experimental study of the Fe-Cr-Mo system has been made using a diffusion couple technique. Both ends of a large number of tie-lines have been determined using both an electron microprobe and a scanning electron microscope with energy dispersive X-ray analysis equipment. The isothermal sections at 1223, 1273, 1373, and 1473 K have been constructed from the experimental data and thermodynamic model calculations. The Gibbs energy of the intermetallic phases has been described with a recently developed model for phases with several sublattices. The parameter values describing the Gibbs energy of each individual phase were determined with a computerized optimization technique. The calculated phase diagrams are in satisfactory agreement with the experimental information and allow reasonable extrapolation outside the experimental temperature range.     

Optimization and Calculation of TbCl3-ACl（A = Li, Na, K, Rb, Cs）Phase Diagrams

Thermodynamic information of the melts involvingrare earth halides and alkali halides plays an importantrole in the preparation of rare earth metals by moltensalt electrolysis and by metallothermic reduction. Theknowledge of thermodynamics of molten s…     

A mathematical model for the solute drag effect on recrystallization

The model for the solute drag effect in phase transformations has been applied to recrystallization, i.e., moving grain boundaries. In this model, the total driving force is dissipated by the interfacial energy, the finite interfacial mobility, the solute drag in boundaries, and diffusion in the matrix ahead of the interface, of which all are taken into account consistently. The effects of the Gibbs energy of segregation and the diffusivity of impurity atoms in boundaries were investigated. The results show that the Gibbs energy of segregation mainly affects the critical composition at which the drastic change in the boundary velocity appears, and the diffusivity of impurity atoms in boundaries mainly affects the velocity reduced by the solute drag effect. In other words, the Gibbs energy of segregation and the diffusivity of impurity atoms in boundaries can be evaluated from experimental data by means of the present model. This model was applied to the Al−Mg system, and the Gibbs energy of segregation and the diffusivity of Mg in boundaries were evaluated from experimental data. The evaluated Gibbs energy of segregation agrees with the estimate based on elastic energy considerations. The diffusivity estimated from this model is smaller than that measured along the grain boundary. ZI-KUI LIU, formerly with the Department of Materials Science and Engineering, Royal Institute of Technology     

A thermodynamic evaluation of the Cr-Fe-N system

The thermodynamic properties of the Cr-Fe-N system have been analyzed using thermodynamic models describing the Gibbs energy of the individual phases. A two-sublattice model has been used for the interstitial solution phases and a substitutional solution model for the liquid phase. The analysis involves a combination of predictions from recent assessments of the binary sides with computerized optimization of new ternary parameters. A set of parameters describing the Gibbs energy of the body-centered cubic (bcc), face-centered cubic (fcc), ∈, CrN, Fe₄N, and liquid phases is given. Using this set of parameters, any type of phase equilibria can be calculated. A number of diagrams are presented comparing the results from the calculations with available experimental data, and the agreement is discussed. Most experimental data are well accounted for. The present study is also compared with a previous evaluation.     

Transition metal alloys of extraordinary stability; An example of generalized Lewis-acid-base interactions in metallic systems

The Engel theory of metals predicts unusually high thermodynamic stability for certain classes of alloys of transition metals for which generalized Lewis-acid-base interactions are possible. To test these predictions, phase equilibria were studied for ternary systems of Zr, C, and the transition metals Re, Ru, Os, Rh, Ir, Pd, Pt, Ag, and Au. Similar literature data for Nb, Ta, Hf, Th, Y, Ce, Er, and Pu with Re, Ru, Rh, Ir, Pt, and Au were evaluated. Thermodynamic data for the carbides of Zr, Hf, Th, Nb, Ta, U, and Y were critically evaluated, tabulated for 1200 to 2300 K, and used to fix the Gibbs energies of formation in kcal/g-atom of alloy, or their limits, for the binary phases of the above metals. In addition, for Zr, activity coefficients and excess Gibbs energies are tabulated. The predicted high stabilities for alloys of Rh, Ir, Pd, and Pt are confirmed with excess Gibbs energies ranging to —100 kcal/g-atom and activity coefficients as low as 10^-12 for zirconium or hafnium in dilute solutions of platinum at 1800 K. Some of the properties of these unusually stable compounds have been measured. An erratum to this article is available at .