ABSTRACT
The first stage in the production of most metallic alloys involves their solidification in a casting process. This chapter deals with how this occurs, from the atomic processes involved in the nucleation and early growth of the solid through to the macrostructure of large castings. The importance of heterogeneous nucleation is emphasized. The reasons for the predominance of cells or dendrites over planar solidification front morphologies are explained, and recalling the equilibrium phase diagrams and diffusion kinetics covered in Chapters 1 and 2, it is shown how this is linked to microsegregation. The thermodynamics and kinetics governing the cooperative solidification of eutectic compositions is covered in detail. The treatment of the macrostructural characteristics associated with solidification in various casting processes and welding includes a description of grain structures and macrosegregation. A brief account of the kinetics of metallic glass solidification is given. Finally, some case studies are discussed.
