ABSTRACT
The development of microstructure in metals takes place by movements of atoms in the crystal lattice, a solid-state mass transfer, which is called diffusion. Most phase transformations are diffusive, i.e., diffusion is required in order for the transformation to take place. The transformation of austenite to pearlite in a carbon steel, through the eutectoid reaction, takes place by the diffusion of carbon atoms in the iron lattice. The deformation of metals at high temperatures, i.e., creep, takes place by mechanisms in which diffusion has an important contribution. Diffusion takes place always in the direction to reduce the free energy. This chapter presents simple analytical solutions to common diffusion problems. It discusses the diffusive flux of a component to be correlated with its concentration gradient. The chapter shows that the driving force for diffusion of a component in a solid solution is the gradient of the chemical potential of that component.
