CONVECTIVE-TRANSPORT PHENOMENA AND MACROSEGREGATION DURING SOLIDIFICATION OF A BINARY METAL ALLOY .2. EXPERIMENTS AND COMPARISONS WITH NUMERICAL PREDICTIONS

Experiments involving the solidification of a Pb-19 percent Sn alloy i n an axisymmetric, annular mold of stainless steel are performed, and results are compared with numerical predictions. Agreement between mea sured and predicted cooling curves is reasonable, although undercoolin g and recalescence, which occur in the experiments, are not predicted by the model. Measured temperatures also indicate that dendrite fragme nts are transported throughout the mold cavity during early stages of solidification, and convection patterns similar to those predicted by numerical simulation can be inferred from the measurements. While ther e is general agreement between measured and predicted trends for macro segregation, the numerical simulation, which assumes axial symmetry, c annot predict the inherently three-dimensional nature of solute redist ribution. Conclusions drawn from temperature and composition measureme nts are supported by metallographic examinations of experimental ingot specimens.