Malin Selleby

Phase Equilibria and Thermodynamic Properties in the Fe-Cr System

Phase equilibria and thermodynamic properties in the Fe-Cr system have been reviewed comprehensively based on experimental information and available computer simulations in different scales. The evaluated phase equilibria show significant differences from the currently accepted thermodynamic description by CALPHAD (calculation of phase diagram) approach. The thermodynamic properties of the Fe-Cr system, such as heat capacity, enthalpy, and activity, have been evaluated in reported experiments. The experiments on phase separation in the Fe-Cr system have also been critically reviewed with a focus on spinodal decomposition. The reported data are concentrated in the temperature range from 673 to 823 K. In addition, there is a transition region between spinodal decomposition and nucleation regimes within the composition limit from 24 to 36.3 at.% Cr and the temperature range between 700 and 830 K. In view of the importance of magnetism in the Fe-Cr system, some inadequacies of the currently used thermodynamic description are pointed out in addition to some problems with the current magnetic model. Remaining issues on the thermodynamics of the Fe-Cr system have been elaborated for future refinement of the thermodynamic description of the Fe-Cr system. According to the present review, the melting temperature of Cr is recommended to be about 2136 K, which is 44 K lower than the value adopted in the research community on thermodynamics, such as the Scientific Group Thermodata Europe.

An assessment of the Ca-Fe-O system

The Ca-Fe-O system is studied with an emphasis on the slag system CaO-FeO-Fe2O3. The compound-energy model is used with ionic species for all solid solution phases. The liquid is described with a special two-sublattice model. The parameters in the models are assessed in order to give an accurate description of the thermodynamic properties of the system, in accordance with all consistent experimental data. The system is described in the temperature range of 298.15 to 2000 K.

Thermodynamic assessment of the MgO-Al2O3-SiO2 system

Thermodynamic properties of the phases in the MgO-Al2O3-SiO2 system were assessed, resulting in a set of self-consistent thermodynamic data. The two ternary Compounds, cordierite and sapphirine, we ...

A reassessment of the CaFeO system

A reassessment of the recently published evaluation of the CaFeO system has been performed. In the previous assessment, liquid Fe2O3 was treated as a basic oxide, while in the present work it is treated as a weak acid. The change has been introduced as a result of difficulties encountered in higher order systems containing silica.

Modelling of acid and basic slags

Abstract There is a worldwide activity on thermodynamic assessment and modelling of oxides. Many different models are tried with varying degree of success. The two-sublattice ionic model for the liquid has been used for several years at our department and some problems, in particular the assessment of acid and basic oxides together with silicates, have occured. These systems are difficult for many reasons, not least due to lack of good experimental data. In this paper some variations in the finer details of the modelling are discussed which should be of relevance in the continuing search for good general thermodynamic models. Many of the systems discussed are still subject to assessment work and there is a need both for new ideas and better cooperation in this field.

Thermodynamic analysis of the Ni-Ta system.

Abstract The thermodynamic properties of the solution and compound phases of the Ni-Ta system were optimized using experimental information on phase diagram and thermochemical quantities. A consistent set of parameters is presented.

A Critical Assessment of Tnermodynamic and Phase Diagram Data for the Al-O System

A critical assessment of the thermodynamic and phase diagram data for the crystalline and liquid phases of the Ge-O system at ambient pressures has been carried out to provide a set of parameters which can be used as a basis for the calculation of ternary and multicomponent phase equilibria. The phase diagram reported by Massalski (Binary Alloy Phase Diagrams, ASM International, Materials Park, 1990) does not correctly reproduce the rather limited experimental information for the system. There is some inconsistency between the rather more extensive experimental thermodynamic data for the three phases of GeO2 stable at ambient pressures.

A thermodynamic database for special brass

In the present work a thermodynamic database for brass alloys is developed. The database may be used to calculate phase diagrams and property diagrams and to simulate solidification, calculations that may be used to develop new alloys and to increase the understanding of existing ones. When developed, such a database reduces the need for further experimental investigations considerably. The present work is focused on so-called special brass (i.e., alloys of Cu and Zn with small additions of, for instance, Al, As, B, Fe, Pb, and/or Si). The database was created using available thermodynamic descriptions and unavailable systems were assessed using the CALPHAD technique. Experimental information was taken from literature and from experimental results obtained in the present work. The database contains the elements Al, Cu, Pb, Si, and Zn. Calculated phase diagrams show that the peritectic reaction in the Cu-Zn system is very sensitive to small additions of Al and Si, which moves the peritectic reaction towards lower Zn contents and higher temperatures.

Thermal expansion and compressibility of Co6W6C

Using powder X-ray diffraction, the pressure-volume (PV) data on Co6W6C were determined at ambient temperature and pressures up to 32 GPa with the following results: isothermal bulk modulus K-300,K ...

An assessment of the Ca-Fe-O-Si system

The thermodynamic properties of the Ca-Fe-O-Si system have been studied with particular emphasis on the slag system CaO-FeO-Fe2O3-SiO2. One of the subsystems, Fe-O-Si, was evaluated simultaneously to be able to take into account the higher order information from the present system. The assessment was succeeded by a study of different modifications of the ionic two-sublattice model that was used to describe the liquid phase. This model allows description of the slag and the liquid metal with one set of parameters. A model has been chosen which is optimal with regard to the fit of experimental data, compatibility with related systems, and number of parameters needed. The assessment is based on recent evaluations of the subsystems. All the solid-solution phases have been described using the compound-energy model.