Computer generation of phase diagrams and the associated free energy curves for a binary system

An interactive computer program is introduced in order to make a simultaneous graphical presentation of phase boundaries and their corresponding free energy curves. The program, which uses a graphics display terminal, is a useful tool in teaching thermodynamic concepts involved in phase diagrams, especially for undergraduate students.     

Modeling of binary molten-salt phase diagrams via neural networks

Computational neural networks are used as implicit thermodynamic models for calculating phase diagrams of binary molten salts. The neural network model accurately describes conformai ionic solution theory in binary systems thereby providing an efficient scheme for determining phase diagrams. Preliminary results are presented formodel AC ₂-BC₂ systems.     

Modeling of binary molten-salt phase diagrams via neural networks

Computational neural networks are used as implicit thermodynamic models for calculating phase diagrams of binary molten salts. The neural network model accurately describes conformai ionic solution theory in binary systems thereby providing an efficient scheme for determining phase diagrams. Preliminary results are presented formodel AC ₂-BC₂ systems.     

TERDIA: Computer program for calculation of ternary phase diagrams for systems of stoichiometric phases using a nonstoichiometric method

A nonstoichiometric method is proposed for calculating ternary or pseudoternary phase diagrams, in which only stoichiometric phases are considered. The simplex method is used for determination of stable triplets of phases (compatibility triangles). These stable triplets of phases and their tie-lines form a relevant phase diagram. This method, which is an alternative to the stoichiometric tie-line construction, is reliable and the numerical process is very fast.     

TERDIA: Computer program for calculation of ternary phase diagrams for systems of stoichiometric phases using a nonstoichiometric method

A nonstoichiometric method is proposed for calculating ternary or pseudoternary phase diagrams, in which only stoichiometric phases are considered. The simplex method is used for determination of stable triplets of phases (compatibility triangles). These stable triplets of phases and their tie-lines form a relevant phase diagram. This method, which is an alternative to the stoichiometric tie-line construction, is reliable and the numerical process is very fast.     

Thermodynamics of binary phase diagrams with a miscibility gap and a congruently melting compound and binary phase diagrams with two miscibility gaps

The thermodynamics of phase diagrams with a miscibility gap and a congruently melting compound and phase diagrams with two miscibility gaps are treated using the Hoch-Arpshofen solution model and the Schottky- Wagner disorder model. We extended the Schottky-Wagner disorder model to the liquid phase. In phase diagrams with two miscibility gaps, a liquid compound between the two miscibility gaps must be present to obtain consistent thermodynamic data. We treated the Rb-I₂, Au-Se, and Sn-S binary systems.     

Thermodynamics of binary phase diagrams with a miscibility gap and a congruently melting compound and binary phase diagrams with two miscibility gaps

The thermodynamics of phase diagrams with a miscibility gap and a congruently melting compound and phase diagrams with two miscibility gaps are treated using the Hoch-Arpshofen solution model and the Schottky- Wagner disorder model. We extended the Schottky-Wagner disorder model to the liquid phase. In phase diagrams with two miscibility gaps, a liquid compound between the two miscibility gaps must be present to obtain consistent thermodynamic data. We treated the Rb-I₂, Au-Se, and Sn-S binary systems.     

Comprehensive handbook of ternary alloy phase diagrams

A program for critical and systematic evaluation of existing ternary alloy phase diagram information by Max-Planck-Institut für Metallforschung, and Alan Prince of the Alloy Phase Diagram Data Committee of the Metals Society, is described. The resulting diagrams and supporting text are planned for publication by Gmelin Institut für Anorganische Chemie und Grenzgebiete as a multi-volume handbook. Described are the procedures to be followed during evaluation and the format to be used for each presentation.     

Computer representation of phase diagrams

The computer representation of phase diagrams is discussed from the point of view of user needs together with the form an ideal system might take for maximum utility. Current work in the field of computer representation of phase diagrams is reviewed and placed in the context of developing a more useful computerized alloy design system. Some new work on computerized interpolation of phase diagram data is also presented.     

Construction of two-dimensional phase fraction charts from ternary phase diagrams

An introduction is presented on how to read two-dimensional, phase fraction charts. Then, a graphical method is outlined that describes how to construct phase fraction charts from ternary phase diagrams.     

Calculation of the binary chromiun-lanthanide phase diagrams

The Miedema model is used to calculate the interaction parameter Ω for binary chromium-lanthanide metal systems in the liquid state. The values of Ω found for the 15 systems range from +21.6 kJ/mol for Cr-Lu to +174.6 kJ/mol for Cr-Eu. The phase diagrams of the 15 systems are calculated using these values and assuming complete immiscibility for the solid state and regular solution behavior for the liquid state. Because of the positive values of Ω, most phase diagrams exhibit a liquid miscibility gap; only the Cr-Er, Cr-Tm, and Cr-Lu systems do not contain a miscibility gap. A comparison is made between the calculated and the experimentally determined Cr-Ce phase diagram.     

二元相图中两个被疏忽的问题

目前在二元相图中普遍存在两个被疏忽的问题:一是关于二元系中许多中间相在某一温度发生晶型转变时如何表示的问题,在已发表的二元相图资料中,大部分用水平实线或虚线来表示这种晶型转变,而二元相图中水平实线或虚线通常是用来表示三相平衡的等温反应,但中间相的晶型转变不是三相平衡的等温反应,所以,不能用实线或虚线来表示;二是对某些沸点较低的组元,在温度高于其沸点温度时,靠近这些组元的端际单相区应该是气相,而许多二元相图中仍然标为液相.本文作者认为应该重视由于疏忽而产生的这两类问题,并加以改正,以免让读者产生误解.     

Comment on thermodynamics of binary phase diagrams with a miscibility gap and a

The Gibbs energy of mixing and the excess Gibbs energy of mixing in the binary systems treated in an earlier study are calculated. In these types of systems, these functions cannot be described by an equation extending between the two end components and also represent the partial quantities correctly.     

Comment on thermodynamics of binary phase diagrams with a miscibility gap and a

The Gibbs energy of mixing and the excess Gibbs energy of mixing in the binary systems treated in an earlier study are calculated. In these types of systems, these functions cannot be described by an equation extending between the two end components and also represent the partial quantities correctly.     

Eutectoid equilibria relationships in binary plutonium phase diagrams

The applicability of a universal relationship of invariant transformations for analyzing eutectoid transformations in binary plutonium systems is demonstrated in this article. This relationship requires a favorable temperature factor for the formation of eutectoid reactions. This work confirms the validity of previously established values for decomposition of δ-phase solid solution and compounds of plutonium with group III-B elements at atmospheric and elevated pressures. It is demonstrated that in alloys of plutonium with elements of group III-B, the parameters of eutectoid transformations of the δ-phase change monotonically with increasing atomic number of the element. For more information, contact Lidia F. Timofeeva at the A.A. Bochvar Research Institute of Inorganic Materials, P.O. Box 369, VNIINM, 123060 Moscow, Russia; fax +7-095-196 4168; tim@bochvar.ru.     

Thermodynamic analysis of some binary phase diagrams involving liquid crystals

A computer-coupled thennodynamic/phase diagram analysis was performed on the phase diagram data of seven binary systems involving liquid crystals. These include five systems based on a homologous series of compounds and two others having 1:1 intermediate compounds. The excess Gibbs energies of the solution phases were thereby calculated, and evaluated phase diagrams were generated that are thermodynamically self-consistent. The results are discussed in the light of what is known about excess solution properties in such systems. The usefulness of the thermodynamic analysis is examined with respect to the prediction of the eutectics of ternary and higher order liquid crystal mixtures. The “Equal G Analysis” is also briefly discussed with reference to the estimation of the nonidealities of mesophase solutions.     

Thermodynamic database of the phase diagrams in Cu-Fe base ternary systems

A thermodynamic database of the Cu-Fe-X [X: aluminum (Al), cobalt (Co), chromium (Cr), manganese (Mn), molybdenum (Mo), niobium (Nb), nickel (Ni), vanadium (V)] systems was developed by the CALPHAD (Calculation of Phase Diagrams) method, where the Gibbs energies of solution phases such as the liquid, face-centered-cubic (fcc), body-centered-cubic (bcc), and hexagonal-close-packed (hcp) phases are described by the subregular solution model, while the those of the bcc phase in the Cu-Fe-Al system and of all compounds are described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, much information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Cu-Fe base alloys.