Abstract
	Recently, large attention is devoted to the research and development of nanostructured materials. These materials with unique microstructure and fine grain size d < 100 nanometres have good physical and mechanical properties.  The outstanding mechanical properties (superstrength, superhardeness, enhanced tribological characteristics, enhanced tensile ductility and superplasticity) are of special importance.  Several different methods for preparing  of nanomaterials are elaborated, some of them based on powder  metallurgy technique.  Residual porosity, pollution of the material system and grain coarsening are the problems that are unresolved satisfactorily up to now.  These negatives can be eliminated by severe plastic deformations (SPD) using the method of the equal channel angular pressing (ECAP) where the experimental material is pressed in special matrix through a special die consisting of two equal channels at the angle of 90°. The formation of high angle nanograins with the specific substructure of lattice and grain boundary  dislocations is studied intensively and  analyzed on models and real material systems, too.
	Hall-Petch dependence as well as evolution of Cu microstructure after severe plastic deformation  (SPD) realised by the method of  the equal channel angular pressing (ECAP) are analysed the present paper. On the basis of experimental results and analyses the different mechanisms of  plastic deformation generation  for coarse grain and nanograin structures were identified.  A final  grain size  decreased from the initial  50 ?m to 100-300 nm after ten ECAP passes.  Mechanical properties before ECAP were Rp0,2=270MPa, Rm=275MPa, Z=65% and after ten passes Rp0,2=464MPa, Rm=475MPa, Z=60%.   Increase and deflection of conventional yield stress  point  were explained by dislocation theory.