Subgrain structure and internal stress fields in UFG materials: problem of Hall–Petch relation

Investigation of the grain and defect structures and mechanical properties of UFG copper with the average grain size 〈 d〉 = 210 ± 120 nm is presented. The microstructural investigations were carried out on foils and replicas using TEM. The internal stresses were measured in grains with different sizes that contained different dislocation structures. It was established that grains with different sizes and defect structures make different contributions to deformation of the material. The parameters of grain boundary sliding were studied in detail. The deformation mechanisms were classified according to their contribution to overall deformation of the UFG copper.