Nanocrystalline Cu with a grain size of 40-60 nm was prepared by severe pla
stic deformation. Active uniaxial tensile deformation of nanocrystalline co
pper at a rate of 10(-5) s(-1) was examined iii situ in the column of an el
ectron microscope. The deformation was established to be realized mainly by
rotation of nanograins and interaction of defects present at grain boundar
ies and in adjacent regions.