LiF-NaF-KF体系的相图计算

基于CALPHAD技术首先评估了LiF-NaF和LiF-KF两个二元熔盐体系,液相和端际固溶体Halite相均采用Redlich-Kister多项式置换熔体模型描述,模型参数的优化选取实验相平衡数据和热化学数据以及本文根据第一性原理预测的数据.结合文献中已报道的NaF-KF体系的热力学参数,用Muggianu模型扩展至LiF-NaF-KF三元体系,根据三元共晶点的实验数据调整三元交互参数.最终的相图计算结果与绝大部分实验数据和第一原理计算数据吻合较好,由此获得了一套自洽且可靠的热力学参数,其能够准确描述LiF-NaF-KF体系的相平衡与热力学性质.     

Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system

Phase equilibrium data of the Ni-Mo-Ta system at 1473, 1373, and 1173 K were determined by means of diffusion triple and electron probe microanalysis (EPMA) techniques in this article. From the present experimental results and literature data, the Ni-Mo-Ta system was thermodynamically assessed using the CALPHAD method. A set of consistent thermodynamic parameters of each phase was obtained. A number of calculated isothermal sections are presented and compared with experimental data. They are in reasonable agreement. The present calculation was successfully used to analyze the solidification behavior of two alloys. Two subsystems, Ni-Mo and Mo-Ta, were assessed prior to the assessment of the ternary system.     

Al—Si—Fe三元合金熔体组元活度的解析

将Ａｌ－Ｓｉ－Ｆｅ三元合金熔体中组元Ａｌ的过剩偏摩尔自由能表达成多项式函数的形式,再由组成该三元系的三个二元子系以及三元系部分实验结果作为边界条件确定多项式中的参数Ａｊｋ值。根据Ｇｉｂｂｓ－Ｄｕｈｅｍ方程导出了计算体系过剩摩尔自由能多项式中的参数Ｆｊｋ值,由Ａｊｋ和Ｆｊｋ值求得组元Ｓｉ、Ａｌ的过剩偏摩尔自由能的表达式,并用上述解析表达式计算出了整个液相区域内各组元的等活度线     

Thermodynamic models of liquid multicomponent metallic solutions

Thermodynamic models for regular, pseudo-regular, subregular, and pseudosubregular metallic solutions are considered. It is shown that the transition from the excess Gibbs energy of a solution to the excess chemical potentials of the components in the subregular solution model leads to more complex dependences of the activity coefficients on the solution composition than those in the regular and pseudoregular solution models. Equations for the excess chemical potentials of components obtained by these models are presented for binary, ternary, and multicomponent solutions. The energy of mixing of components in binary solutions are calculated and estimated using experimental data obtained by various authors for the last half a century. The zero-order and first-order interaction parameters are estimated from the energy parameters for dilute solutions.     

Thermodynamic Modeling of the Al-Ti-V Ternary System

The sub-binary systems Al-Ti, Ti-V, and Al-V are reviewed and adopted from the previous assessments, the thermodynamic analysis of the Al-Ti-V ternary system is performed by the CALPHAD approach, and a set of self-consistent thermodynamic parameters of the ternary system are obtained. Furthermore, the isothermal sections of this system at 1073 K, 1173 K, 1273 K, 1373 K, and 1473 K (800 °C, 900 °C, 1000 °C, 1100 °C, and 1200 °C) and the ternary invariant equilibria are calculated and compared with the corresponding experimental data, and all are in good agreement with most of the experimental results. Thus, the optimized thermodynamic parameters in this study may provide more accurate guidance to develop the new alloys involving it.     

Representation of thermodynamic properties of multi-component systems using interaction parameters

Integral excess free energy of a multi-component – ternary system has been expressed in terms of the Maclaurin infinite series. The series is subjected to appropriate boundary conditions and each of the derivatives correlated to the corresponding interaction parameters. The partial thermodynamic property of component 1 derived by the use of logarithmic functions together with a geometric progression is presented. The equation is found to be capable of interpreting thermodynamic data over a wide compositional range of the ternary system and is independent of compositional paths. An alternative approach for the determination of generalised relations between interaction parameters to that of Lupis and Elliott has been developed.     

Model Uncertainty in Normalized Shear Modulus and Damping Relationships

Model uncertainty associated with normalized shear modulus and material damping ratio relationships developed in a previous study is discussed in terms of standard deviations in this paper. The relationships were originally developed by separating resonant column and torsional shear test results of 122 specimens into three general geologic groups (Quaternary-age soils, Tertiary-age and older soils, and residual/saprolite soils) and determining mean regressional model parameters (i.e., α, k, γr1, and Dmin1) for each group. Statistical variability of the regressional parameters is quantified and expressed by standard errors of prediction. The determined uncertainty of the regressional parameters is then propagated through the recommended relationships using the point-estimate method to estimate the model uncertainty of the relationships. The point-estimate method is a simple and effective method of uncertainty propagation. For uncertainty estimation, the regressional parameters are assumed to be uncorrelated for the sake of simplicity. The influence of this assumption on the model uncertainty of normalized shear modulus and material damping ratio values, as well as the sensitivity of the model uncertainty to the uncertainty of various regressional parameters, are also discussed.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CaO-Al2O3, Al2O3-SiO2, and CaO-Al2O3-SiO2 systems

All available thermodynamic and phase diagram data have been critically assessed for all phases in the CaO-Al₂O₃, Al₂O₃-SiO₂, and CaO-Al₂O₃-SiO₂ systems at 1 bar pressure from 298 K to above the liquidus temperatures. All reliable data for the binary systems have been simultaneously optimized to obtain, for each system, one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasichemical model was used for the slag. With these binary parameters and those from the optimization of the CaO-SiO₂ system reported previously, the quasichemical model was used to predict the thermodynamic properties of the ternary slag. Two additional small ternary parameters were required to reproduce the ternary phase diagram and ternary activity data to within experimental error limits. The calculated optimized phase diagram and thermodynamic properties are self-consistent and are the most reliable currently available estimates of the true values.     

The thermodynamics of the Fe–Co–S ternary system

The thermodynamic properties of the Fe–Co–S ternary system were determined by equilibrating the system with a known sulphur pressure established by using a gas mixture of H₂S/H₂ at 1473, 1548 and 1623 K. The iso-activity contours for Fe and Co were established by application of the Gibbs Duhem equation using Schuhmann’s method for ternary systems. For this purpose a computer program was used to calculate the activities of iron and cobalt. The cobalt activity coefficients in dilute solutions of cobalt in the iron–cobalt–sulphur system, which are of industrial interest, were determined. From the experimental data, the partial heats of solution for iron, cobalt, and sulphur and the integral heats of solution for the Fe–Co–S ternary systems were derived.     

Integral treatment for the representation of thermodynamic properties in multicomponent systems using interaction parameters

The partial thermodynamic functions of the solvent component of a ternary system have been deduced in terms of the interaction parameters by integration of several series which emerge from the Maclaurin infinite series based on the integral property of the system and subjected to appropriate boundary conditions. The series integration shows that the resulting partial functions are suitable for interpreting the thermodynamic properties of the system and are independent of compositional paths. In the present analysis, the higher order terms of these series are found to make insignificant contributions. Formerly Visiting Professor, Technical University Berlin     

A Thermodynamic Approach to a Density Model for Oxide Melts

In an attempt to estimate the densities of complex slags, a model based on the thermodynamics of slags developed earlier by the present authors is extended to ternary and multi‐component systems in the present work. The molar volumes of ternary and higher order systems were derived from the relative integral molar enthalpies of mixing of the corresponding slags. The higher order of slag systems has been predicted by using the parameters from the related binary sub‐systems, which have been evaluated earlier. Comparisons of calculated results with experimental data on molar volumes available in literature show a satisfying agreement for a number of systems, within the limits of experimental uncertainties. The model presents a promising method to compute the molar volume of slag systems where no experimental data is available using the abundance of thermodynamic data available. The model would also enable the generation of density data for slags containing Al₂O₃, CaO, FeO, MgO, MnO, and SiO₂ compatible with the corresponding thermodynamic data.     

Experimental investigation and thermodynamic modeling of the Cr-Ni-Si system

The constitution of the Cr-Ni-Si ternary system is established via experiment and thermodynamic modeling. In the experimental section, 35 decisive alloys, the compositions of which are based on a preliminary calculation using available literature data, are prepared by arc melting of cold-pressed pellets and annealing at 900 °C for 25 days. Water-quenched samples are analyzed by using X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques. In the modeling section, a consistent thermodynamic data set for the Cr-Ni-Si system is obtained by considering the present experimental results and reliable literature data. Comparisons between the calculated and measured phase diagrams show that the experimental information is satisfactorily accounted for by the thermodynamic modeling. The liquidus projection and reaction scheme for the entire ternary system are presented.     

Composition Range of Amorphous Mg-Ni-Y Alloys

Based on the thermodynamic point of view, a method for predication of the composition range of amorphous ter-nary alloys was proposed. The composition range of amorphous ternary alloys is determined by the comparison of the excess free energy of the amorphous alloy and the free energy of competing crystalline states. The free energy is extrapolated from the data of three binary alloys by using Toop‘s model. The method was applied to predict the composition range of amor-phous Mg-Ni-Y alloys. The theoretical results are in good agreement with the available experimental results. It indicates that the present method can be used to predict the composition range for amorphous ternary alloys.     

Nb-Ti-Si三元系1 173 K等温截面的测定

运用扩散偶技术并结合电子探针微区成分分析方法，对Ni-Ti-Si三元扩散偶进行了相分析，测得了Ni-Ti-Si三元系1173K下所生成的7个扩散层，即TiSi2、TiSi、Ti5Si4、Ti5Si3、Ti3Si、Nb5Si3和NbSi2；未发现在元化合物。根据实验所得的结线数据并结合扩散偶中的相区分布规则，得出了Nb-Ti-Si三元系1173K下的等温截面。