Comparison of Thermodynamic Models Applied to Al-Mg-Zn Melts

Existing literature on the thermodynamic properties of the molten Al-Mg-Zn system provides an opportunity for assessing models for predicting ternary-system data with binary-system values. An important facet of such modeling is the use of the Gibbs-Duhem relationship; mathematical expressions have been developed to replace the traditional graphical method. Another important facet is the choice of binary-system study; in some systems, the type of study can make a difference in the results. Six models were chosen for investigation: the regular, subregular, and quasi-regular solution models, along with the empirical equations developed by Margules, Kohler, and Colinet. The modeling results show good agreement with actual experimental data from studies of the Al-Mg-Zn ternary system; the choice of which binary-system study is used to provide data for the model makes as significant a difference in the modeling results as the choice of model itself. © 1988 American Chemical Society.