Two-dimensional modelling and experimental study on microsegregation during solidification of an Al–Cu binary alloy

To explain the experimentally observed relation between the cooling rate and the non-equilibrium eutectic fraction obtained during solidification experiments of Al–Cu binary alloys [Eskin DG, Du Q, Ruvalcaba D, Katgerman L. Mater Sci Eng A 2005;405:1–10], a two-dimensional (2-D) microsegregation model, the pseudo-front tracking (PFT) method [Jacot A, Rappaz M. Acta Mater 2002;50:1909–26, Jacot A, Rappaz M. Acta Mater 2002;50:3971, Du Q, Jacot A. Acta Mater 2005;53:3479–93], is employed. The analysis of simulated solidification kinetics, including the grain morphology evolution, coarsening and back diffusion, reveals the pronounced effect of dendrite coarsening on the final non-equilibrium eutectic fraction. Because the 2-D modelling can describe rigorously how the important microstructure feature – dendrite arm spacing – evolves, its predictions are in good agreement with the trend observed in the experiments, which both the classic Brody–Flemings model and the 1-D PFT model have failed to explain.