On cooling rates, interface velocities and particle sizes in spray atomization

A detailed characterization of spray-atomized powders of Al80Fe10V4Si6 showed that the refinement in microstructure was significantly affected by the size of the powder particles. A polished section of powder particles, exhibiting fine dendrites evolved during solidification, was used as an illustrative example. The particles invariably showed nucleation on the surface of the droplet, indicating the possibility of solid-liquid interface proceeding from one side of the powder particle to the diametrically opposite side. The microstructure changed from cellular to dendritic away from the nucleation center. The combined effect of growth rate of solid and thermal gradient in the liquid influenced the solidification morphology of the powders.