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Abstract
An earlier procedure for calculating homogenization during the solidification of binary alloys is extended to include more realistic assumptions for dendrite arm coarsening kinetics and the partition coefficient. Dendrite coarsening is shown to follow the usual exponential function which differs from that relating final dendrite arm spacing λf to local solidification time. This function is not sensitive to the assumption for the partition coefficient or the choice of initial spacing (between λ0 = 0 and λf/2). The homogenization parameter H (normalized difference between the minimum possible concentration and the actual minimum concentration in the centre of the dendrite arm) changes only slightly with the partition coefficient. With the average coarsening parameter used by earlier authors, homogenization is overestimated and a lower amount of the non-equilibrium phase is obtained. The experimental data available for Al–Cu alloys in the range 2–20 wt-% Cu are very closely predicted by the numerical procedure used here.
MST/435