Numerical investigation on the motion of free-floating crystals during dc casting of aluminum alloys

Abstract

Macrosegregation formed during direct chill (DC) casting of aluminum ingots will deteriorate the mechanical property of products. The characteristic of macrosegregation is reported to be affected by the free-floating crystals, which was proved to result in the center negative segregation. The motion of free-floating crystals in ingots is numerically simulated. The model is developed to incorporate fluid flow, heat transfer, and the motion of free-floating crystals basing on the mixture model and Lagrangian approach. Efforts are made to investigate the motion of free-floating crystals in liquid and slurry zones during solidification of casting process. In addition, distribution of the dendrites in mush and solidified zones is also studied. The variation of macrosegregation with the influence of free-floating crystals can be primarily clarified according to the results.