All current models used to predict ternary thermodynamic properties from binaries improperly assume that the selected binary compositions in a ternary model are independent of ternary considered. As a result, it will require human interference for selecting models and arranging components to three apexes of a triangle, and will lead to an unacceptable result in some limiting case. A reasonable assumption should be that the selected binary compositions are closely related to the ternary itself. On the basis of this idea, a completely new model has been suggested. It seems that this new model is more reasonable theoretically from consideration, more reliable in practical application and more realistic to use in computerized thermodynamic and phase diagram calculation.

A general solution model for predicting ternary thermodynamic properties

During the past 3 decades, all solution models that were used to predict thermodynamic properties of a multicomponent system from binaries improperly assumed that the selected binary compositions in a model are independent of the practical system to be treated. This assumption causes problems both in symmetrical and asymmetrical models. In this article, a new solution model has been suggested, which gets rid of this traditional way and assumes that the selected binary compositions should be closely related to the system considered. After introducing a new concept, the “similarity coefficient,” the relation between the selected binary compositions and the composition of the multicomponent system is established and a new model is generated. This new generation model is more reasonable in theoretical considerations, more reliable in practical use, and more realistic in computerization for estimating thermodynamic properties and calculating phase diagrams in a multicomponent system.

A new generation solution model for predicting thermodynamic properties of a multicomponent system from binaries

Intra-granular Acicular Ferrite (IAF), as one of the most well-known desirable microstructure of ferrite with a chaotic crystallographic orientation, can not only refine the microstructure and retard the propagation of cleavage crack but also provide excellent combination of strength and toughness in steel. The effect of adding cerium on microstructure and controlling proper cerium-based inclusions in order to improve properties in low-carbon commercial steel (SS400) were investigated. The type of inclusions can be controlled by changing S/O ratio and Ce content. Without Ce modification, MnS is a dominate inclusion. After adding Ce, the stable inclusion phases change from AlCeO3 to Ce2O2S. The optimum amount of cerium, 0.0235 wt.%, lead in proper grain refinement and formation of cerium oxide, oxy-sulfide and sulfide inclusions. Having a high amount of cerium results in increasing the number of inclusions significantly as a result it cannot be effective enough and the inclusions will act like barriers for others. It is found that the inclusions with a size of about 4∼7 μm can serve as heterogeneous nucleation sites for AF formation. Thermodynamic calculations have been applied to predict the inclusion formation in this molten steel as well, which show a good agreement with experimental one.

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Effect of Adding Cerium on Microstructure and Morphology of Ce-Based Inclusions Formed in Low-Carbon Steel.

In the previous paper, we have presented a new method for calculating ternary thermodynamic properties based on three binaries. This new model can overcome the inherent defects for both current symmetrical and asymmetrical models and can combine two kinds of current models into one. More important, it can eventually realize the computerization for calculating thermodynamic properties and phase diagrams for multicomponent systems. In this paper we will give this new model a new formalism based on binary regular-solution type parameters. When this model is applied, all we need to do is substitute these parameters into formulae presented here and evaluate them by using a simple calculator. Since a large number of real systems can be approximately fit through a regular-solution type model, therefore, this new formalism is significant.

Formalism of new ternary model expressed in terms of binary regular-solution type parameters

A thermodynamic analysis of phase equilibria in the Fe-N-V system has been carried out on the basis of the established three binary descriptions and selected ternary experimental data. The two-phase equilibrium between austenite and VN phase was treated as a portion of the miscibility gap in the fcc phase. A set of isothermal sections was presented in the whole range of compositions. Some thermodynamic analysis was carried out on the solubility products of VN in ferrite and austenite.

A thermodynamic assessment of the Fe-N-Ti system

A new solution model named integration Model has been developed for predicting the ternary thermodynamic properties from its binary ones. This model is more reasonable for its full utilization of binary information. Binary thermodynamic properties are fitted by means of rational function method and ternary partial thermodynamic properties are calculated using R-function method. Integration model was applied to the Na-Hg-Pb system and a good accordance was obtained between the calculated and experimental values.

Integration model predicting ternary thernodynamic properties from binary ones

New formulae for calculating activities and activity coefficients from phase diagram at a fixed temperature are presented for a binary system involving a two liquid or solid coexisting phases. In the new formulae. Richardson's assumption that for many systems Δ H i Δ S E i is approximately equal to 3000, has been adopted. In terms of the new formulae, activities of components in Zn-Pb and Zn-Bi binary systems are calculated and the results show that the formulae are efficient.

A new treatment for calculating activities from phase diagrams involving two liquid or solid coexisting phases

The formulae for calculating activities and activity coefficients from the phase diagram involving a two liquid or solid coexisting phases have been presented, in which no extra thermodynamic properties are required except for the composition of components along a miscibility gap. The application of these equations to the Zn-Pb and Zn-Bi systems shows that the calculation results are close to the experimental measurements.

Calculation of activities from the phase diagram involving two liquid or solid coexisting phases

Oxidation kinetics of TiN-containing composites

Thermodynamic condition of rare earth cerium inclusion formed in spring steel used in fastener of high-speed railway was studied by the thermodynamic calculationIn addition,the effect and condition of rare earth cerium on modifying Al2O3 inclusion were analyzedThrough the standard Gibbs free energies of formation of the sulfides,oxides and oxysulfides of cerium,the precipitation diagram in space was builtAnd it was applied to predict the sequence of rare earth inclusion formed the spring steelFinally,the ultimate state of rare earth inclusions and their thermodynamic transformation condition were determinedThe computation results show that the most easily formed inclusion is CeAlO3 when rare earth element Ce is added to the molten steel,with Ce2O2S followingIn this work,when the activities of oxygen and sulfur in the steel are 0000 639 and 0005 845,respectively,the first precipitated inclusion is Ce2O2SMoreover,when the aluminum content in the steel is 0013%,the theoretic amount of added rare earth Ce is 00019%,which can realize Al2O3 deformation

Chou Kuo-Chih

Papers

Integration model predicting ternary thernodynamic properties from binary ones

A new treatment for calculating activities from phase diagrams involving two liquid or solid coexisting phases

Calculation of activities from the phase diagram involving two liquid or solid coexisting phases

Oxidation kinetics of TiN-containing composites

Thermodynamic analysis of cerium inclusion formed in spring steel used in fastener of high-speed railway