Databases multi-component

Chapter 10 provides an exhaustive description of how these techniques can be applied to a large number of industrial alloys and other materials. This includes a discussion of solution and substance databases and step-by-step examples of multi-component calculations. Validation of calculated equilibria in multi-component alloys is given by a detailed comparison with experimental results for a variety of steels, titanium- and nickel-base alloys. Further selected examples include the formation of deleterious phases, complex precipitation sequences, sensitivity factor analysis, intermetallic alloys, alloy design, slag, slag-metal and other complex chemical equilibria and nuclear applications. 

This approach works well for systems where no neutral ions exist and a database for the system (Li, Na, K)(F, Cl, OH, CO3, SO4) has been developed (Pelton 1988) which gives good estimates for activities in multi-component liquids. However, the above approach is more limited in the presence of neutral ions which are necessary if one wishes to model ionic liquids which may contain neutrals such as S. 

The main areas of application for more generalised models have, until recently, been restricted to binary and ternary systems or limited to ideal industrial materials where only major elements were included. The key to general application of CALPHAD methods in multi-component systems is the development of sound, validated thermodynamic databases which can be accessed by the computing software and, until recently, there has been a dearth of such databases. 

The understanding of the critical systems in an assessed database is in the hands of the developer of the database and can often only be understood after a series of multi-component calculations are made. 

Only after at least these three steps are taken can a database then be considered as an assessed database and used with confidence in an application involving a complex multi-component alloy. 

Calculation of sulphide capacities of multi-component slags. The thermo-dynamics and kinetics of desulphurisation are of great importance to iron and steel making and the ability to predict the behaviour of sulphur associated with multi-component slags is, therefore, very desirable. To this end Felton et al. (1993) recently described an approach to predict the sulphide-removing capacity in multi-component oxide slags. While a comprehensive database for oxides was already available, the inclusion of S had not yet been undertaken. Therefore it was not possible to calculate the necessary S activity and solubility directly throi h a... 

The vapour pressure data (from a physical properties database capable of carrying out multi-component estimations) has been plotted as a straight line on Figure 6.4. This allows the temperatures at the relief pressure and maximum pressure to be read off. The rates of temperature rise at these pressures can also be read off. These values are given in Table 6.2. 

Surface complexation is a typical multi-component reaction, similar to cation exchange. The database for surface complexation includes complexation constants for major elements in groundwater such as and S04 , but not for and HCOs". In the first instance, constants for these ions can be estimated with linear free energy relations (LFER s) in which the properties of similar chemical systems are compared and interpolated (Dzombak and Morel, 1990). Thus, the surface complexation constant for is expected to lie in between the ones for and for Zn, in line with the known differences of the association constants of these heavy metals with OH in water. For the weak sites, the LFER gives ... 

This recently-established, multi-component database is available through ECHO, the European Communities Host. It holds details of Cbmmunity Research and Technological (RTD) activities, especially those included in the EC s R D Framework Programme. Details of reports listed in European Abstracts (EARS) form part of CORDIS in addition to being available in printed format. 

The data listed in the tables in Part VII also form the database for EQUITHERM, a software system authored by I. Barin, G. Eriksson, F. Sauert, M. Zeitler, B. Wittig, and W. Schmidt, which is available from the publishers of the book. EQUITHERM can be used to carry out thermodynamic calculations on multi-component, multi-phase systems made up of any of the substances listed in this work. Thus, the publishers are in the unique position of being able to offer both a printed compilation of thermodynamic data for pure substances and a software package for the calculation of equilibria in multi-species systems. 

FactSage, with its modules to manipulate thermochemical databases and to calculate complex equilibrium states as well as multi-component phase diagrams, has been applied for the data compilation and assessment work described below as well as for the generation of the graphical results presented further below. 

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