Microstructure and mechanisms of its formation in submicrocrystalline copper produced by severe plastic deformation

The results of comparative electron-microscopic examination of the grain and defect microstructure produced in submicrocrystalline copper by the methods of equal-channel angular (ECA) pressing and torsion in Bridgman anvils are presented. It is found that the general feature of defect substructures in the submicrocrystalline state forming upon severe plastic deformation is the presence of highly defect structures with a high crystal-lattice curvature, high continuum density of disclinations in the bulk of microcrystals, and high density of these defects at their boundaries. An analysis of fields of local internal stresses was performed for these states. Under conditions of torsion under pressure, a more intense fragmentation of crystal lattice in comparison with the ECA pressing and a higher anisotropy of misorientations and sizes of submicrocrystals were found. The nature of the above features and mechanisms of crystal-lattice reorientation upon the formation of sibmicrocrystalline states are discussed.