On the basis of a multi-length scale modeling,a mixture-averaged multi-component/multiphase microsegregation model was proposed without pre-set function for the micro-scale solute profile.The model explains the effect of morphologies of solidifying phases and solid back diffusion (SBD) on segregation,and covers the two limiting solidification cases of Scheil and Lever-rule models.A commercial Thermo-Calc software package/database was linked to the algorithms via its TQ6-interface for instantaneous determination of the related thermodynamic data of the multi-component alloys.The influences of cooling rate and other parameters on the solidification path and micro-segregation behavior were numerically investigated by sample calculation of the ternary Al-Cu-Mg alloys.A parallel experimental investigation on Al-Cu-Si alloys solidified under different cooling conditions was conducted to validate the theoretical model.Reasonable agreements were gained between the predicted solidification paths and the measured results.