A model for predicting the microsegregation of ternary alloys was developed via extending a previously proposed unified microsegregation model for binary alloys. The present multicomponent/multiphase model retains the advanced features of the previous binary microsegregation model, in which the unified microscale parameter Φ takes a general function form to account for more possible influential factors, including the partition coefficient, solid fraction, solid diffusion coefficient, dendrite geometrical morphologies and solidification rate, etc.

The algorithms fr cacuating the solidification paths of ternary isomorphous and eutectic alloys were proposed, which closely couples with a commercial software package/database of Thermo–Calcvia its TQ6–interface in order to directly access to thermodynamic data needed in the multicomponent/multiphase solidification path computations. In the solidification of primary phase and three phases eutectic, solid fraction f_s was selected to be a control variable when solving the equations of the microsegregation models, while in the solidification of two phases eutectic, temperature was selected to be a control variable as the relationship between the concentrations of solutes B and C was unknown. In each calculation iterative step, the names and number of the equilibrium phases were obtained from Thermo–Calc, and then saved and compared with the calculation results of the previous step. As the names and number of the equilibrium phases in each solidification stage of ternary eutectic alloys are different, the three solidification types were determined by comparing with the results in the computation process.

The availability and reliability of the proposed multicomponent/multiphase model and algorithms were demonstrated by sample computations for the solidification paths of Fe–40V–40Cr, Al–4.5Cu–1Si, Al–10Cu–2.5g and Al–1.49Si–0.64Mg (mass fraction, %) alloys under different solidification/cooling rates, and by comparisons with the experimental results of quantitative measurementof corresponding solidification microstructures.