The morphological evolution of equiaxed dendritic microstructures during coarsening

The morphological evolution of equiaxed Al-20 wt. %Cu dendritic microstructures was studied in three dimensions. The microstructure evolved into a highly interconnected structure, where the inverse specific surface area scaled linearly with the cube root of time. As the size scale of the microstructure increased during coarsening, the scaled morphology of the interfaces changed only slightly. The distribution of interface normals indicated that the microstructure was approximately isotropic. These results are in contrast to those found using a directionally solidified Al-Cu alloy of a similar solid volume fraction, where the structure evolved into solid cylinders parallel to the growth direction used to create the sample prior to coarsening. Thus, we find that the initial morphology of a dendritic structure can have a major impact on its morphological evolution.