Influence of Transport Mechanisms on Macrosegregation Formation in Direct Chill Cast Industrial Scale Aluminum Alloy Ingots

Abstract

AbstractThe phenomena responsible for the formation of macrosegregations and grain structures during solidification are closely related. We present a model study of macrosegregation formation in an industrial sized (350 mm thick) direct chill (DC) cast aluminum alloy slab. The modeling of these phenomena in DC casting is a challenging problem mainly due to the size of the products, the variety of the phenomena to be accounted for, and the nonlinearities involved. We used a volume‐averaged two‐phase multiscale model that describes nucleation on grain refiner particles and grain growth, fully coupled with macroscopic transport: fluid flow driven by natural convection and shrinkage, transport of free‐floating equiaxed grains, heat transfer, and solute transport. The individual and combined roles of shrinkage, natural convection, and grain motion on the sump profile and macrosegregation formation are analyzed. The formation and evolution of grains are discussed. We show that it is important to account for all the named transport mechanisms to be able to explain the macrosegregation pattern observed experimentally in DC cast ingots.