Settling of multisized clusters of alumina particles in liquid aluminum

The clustering of alumina particles during their incorporation into pure liquid aluminum by stirring was studied experimentally. It was found that these particles together with entrained oxide films formed clusters of various sizes and shapes. When the stirring stopped, these clusters settled to form a loose sediment (containing about 0.18 volume fraction of alumina) on the bottom of the crucible. A mathematical model was developed to describe the settling of multisized clusters. Information regarding the size distribution of the clusters was obtained by matching the model results with the experimental data. The size distributions of the alumina clusters were comparable to those estimated from metallographic measurement.