Solidification Phenomena: Dendrites and Constitutional Supercooling

This lecture covers the solidification processes of pure metals and alloys, focusing on the formation of dendritic structures. It begins with an introduction to solidification, explaining how pure metals typically solidify against a cold mold, leading to planar front growth under specific thermal conditions. In contrast, alloys generally solidify by forming dendrites, with columnar structures at the edges and equiaxed structures at the center. The concept of constitutional supercooling is introduced, highlighting how it affects the stability of the solidification front. The lecture further explores various cases of alloy solidification, including the impact of thermal gradients and diffusion on the solidification process. It discusses experimental setups, such as the Bridgman furnace, to control solidification parameters. The lecture concludes with a summary of the differences in solidification behavior between pure metals and alloys, emphasizing the conditions that lead to stable or unstable growth of solidification fronts.