Microsegregation in a binary alloy solidified in the form of deep cells is predicted using a simplified finite difference
model. The model accounts for solid state diffusion and for flow of liquid between cells driven by solidification shrinkage.
Cell tip undercooling is predicted using the expression originally derived by Bower
et al. Cells are assumed to be cylindrical, and solid state diffusion along the cell axis is ignored, simplifying considerably prediction
of solid state diffusion and cell shape behind the tip, which are treated as a one-dimensional moving boundary problem. Experiments
were conducted on binary Al-4.5 wt pct Cu, solidified in the cellular growth regime using a Bridgman furnace. Microsegregation
in the samples was measured and is compared to predictions; good agreement is found, both for cell heights and microsegregation
in the fully solidified material. It is found that intercellular fluid flow exerts a small, but discernable, influence on
microsegregation and cell shape.
Formerly Research Assistant, Department of Materials Science and Engineering, Massachusetts Institute of Technology