A study of ultra-fine grained Cu produced by high-pressure torsion was presented. Positron annihilation spectroscopies (slow positron implantation, lifetime and Doppler broadening spectroscopies), transmission electron microscopy, X-ray diffraction spectroscopy, and microhardness measurements were used to identify defects and their spatial distribution, i.e. lateral distribution and depth profile, in the specimens. Two types of defect could be identified: dislocations in the distorted regions along grain boundaries and micro-voids of size of 3-4 vacancies within the grains. No change in grain size as a function of the distance from the center of the sample disk was observed. The mean coherent domain size close to the surface was found to be 80nm and it increased slightly with depth. The concentration of micro-voids was found to decrease with depth and varied slightly with the distance from the center of the disk, being lowest in the center. No position dependence of the concentration of dislocations was observed.

Spatial Distribution of Defects in Ultra-Fine Grained Copper Prepared by High-Pressure Torsion. J.Cížek, I.Procházka, G.Brauer, W.Anwand, R.Kužel, M.Cieslar, R.K.Islamgaliev: Physica Status Solidi A, 2003, 195[2], 335-49