Nucleation of new grains in recrystallization of cold-worked metals

Abstract

Recent experimental evidence on the process of nucleation is reviewed. This suggests that nuclei develop from sub-grains situated in regions where there is a rapid change of orientation, either due to the original grain-boundaries or to transition bands introduced inside grains by deformation. Development of large sub-grains capable of growth at grain-boundaries may be stimulated either by a coalescence of sub-grains adjacent to old grain-boundaries, or at grain edges, by a process of re-establishing the equilibrium angles distorted by deformation. Further understanding of nucleation will require investigation both of the nature of the cold-worked state in polycrystalline materials and also of the mobility of general low-angle boundaries (θ less than 15 °).