X-ray peak profile analysis was employed to determine the crystallite size distribution and the evolution of dislocation type and density in pure Cu deformed by rolling at liquid nitrogen temperature for the following rolling reduction levels: 67, 74, 87 and 97%. The results show that as the deformation level increased, the variance and the median of the crystallite size distribution decreased. It was also found that the dislocation density decreased in the first segment of the deformation, and increased slightly after reaching a minimum. This could be explained by the fact that the mobility of the dislocations was limited by the low deformation temperature. In order to reduce the strain energy, the dislocations reorganize themselves into dislocation cell structure, which leads to the reduction of the X-ray coherent domain length. Furthermore, it was established that full dislocations dominate the deformation process at lower deformation levels, when the median of the crystallite size distribution was greater then 50nm. At higher deformation levels and smaller crystallite size, the fraction of partial dislocations become significant, while the overall dislocation density increased slightly and the population of the full dislocation decreased. It was concluded that the increase in dislocation density was due to the emission of a new generation of partial dislocations, which become the leading deformation mechanism.

X-Ray Peak Profile Analysis of Crystallite Size Distribution and Dislocation Type and Density Evolution in Nano-Structured Cu Obtained by Deformation at Liquid Nitrogen Temperature. I.C.Dragomir, M.Gheorghe, N.Thadhani, R.L.Snyder: Materials Science and Engineering A, 2005, 402[1-2], 158-62