Introduction

Various processes of microstructural evolution that occur during annealing are introduced, with a focus on changes in the grain structure. Grain growth is driven by the excess free energy associated with grain boundaries. This may occur uniformly or heterogeneously, in which case it is known as abnormal grain growth. Recrystallization is driven by the excess free energy associated with dislocations stored during plastic deformation. Depending on the circumstances, this is variously known as primary recrystallization, secondary recrystallization, dynamic recrystallization, or meta-dynamic recrystallization. Recovery is the process by which dislocation density decreases without long range motion of boundaries and is often accompanied by the formation of subgrain networks that replace the tangled dislocation structures formed during deformation. Dynamic recovery is the set of processes that decrease dislocation density during the deformation, as opposed to subsequent annealing. The historical development of recrystallization as a topic of research is briefly reviewed along with relevant literature.