Introduction

Most of the processes studied in this chapter involve transport of matter across an interface while a phase transformation also takes place at this interface, all under conditions of morphological stability and in the solid state. The interaction between the diffusion process and the interface reaction is of great interest and we develop the coupling between the two processes. Also, we consider processes that involve matter transport to an interface with a divergence of this transport at the interface. We do not explore the latest results of studies of each phenomenon considered in this chapter. To do so would involve book length reviews of each and is obviously not in the scope of this introductory text. Rather, we limit ourselves to a development of the coupling between the various transport phenomena in order to emphasize their significant physical aspects. An important factor in this coupling of atom transport to and/or from an interface and the interface reaction is the stress developed ahead of the moving interface due to a gradient of composition. Most theories of moving interface processes have not included stress as a factor. In many of these processes, non-equilibrium thermodynamics contributes a formalism that is often useful in defining the relations between parameters.

1. Diffusion Couple (Alpha/Beta), No Intermediate Phase