Recovery After Deformation

This chapter is concerned only with recovery, which occurs on annealing after prior deformation. The term recovery refers to changes in a deformed material that occur prior to recrystallization, and which partially restore the properties to their values before deformation. It is now known that recovery is primarily due to changes in the dislocation structure of the material, and in discussing recovery it is most convenient to concentrate on the microstructural aspects. Recovery is not confined to plastically deformed materials, and may occur in any crystal into which a non-equilibrium, high concentration of point or line defects has been introduced. Well known examples of this are materials that have been irradiated or that have been quenched from high temperatures. In these situations, recovery will occur on subsequent annealing and this may restore the properties and microstructure completely to the original condition. During recovery, the microstructural changes in a material are subtle and occur on a small scale. The microstructures as observed by optical microscopy do not usually reveal much change and for this reason, recovery is often measured indirectly by some bulk technique.