A numerical model has been developed to predict the element distribution and some microstructural features in dendritically solidified binary and ternary alloys. Phase diagrams calculated on the basis of thermodynamic functions are taken into account. Thus, a minimum of assumptions is needed to describe the equilibrium at the solid/liquid interface, the partition coefficient of an alloying element is allowed to change as a function of temperature and concentration of other alloying elements.
The description of the equilibrium at the interface appears to be highly significant. Assuming a constant partition coefficient may be justified for some binary alloys, but the assumption has to be verified for each system. Small additions, like dopants or impurities, influence the position of equilibria in phase diagrams, thus requiring the treatment of basically binary alloys as multicomponent systems. In ternary or higher order alloys the assumption of constant partition coefficients leads to erroneous results. For microsegregation predictions in technical alloys realistic phase diagrams have to be taken into account.