Scanning X-ray diffraction peak profile analysis in deformed Cu-polycrystals by synchrotron radiation

Densities and arrangements of dislocations and mesoscopic long-range intern al stresses in cold-rolled polycrystalline copper were determined in scanni ng mode by X-ray peak profile analysis with synchrotron radiation. The high brilliance enabled the use of a focal spot of less than 50 mu m. The diffr action profiles of the 200 reflections were measured by scanning the specim en step by step in front of the beam. In this way, the heterogeneities of t he deformation-induced microstructure within single grains were obtained. A t small deformations including stage III, the dislocation densities and the internal stresses were uniform within the grain interior, but larger near the grain boundaries where the dislocations showed a tendency to form stres s-intensive arrangements. At higher deformations towards and in stage IV, t he dislocation density and the internal stresses increasingly fluctuated wi thin the whole grain. The fluctuations were interpreted as the transformati ons of polarized dipolar dislocation walls (PDW) into polarized tilt walls (PTW) observed recently by macroscopic diffraction experiments on highly de formed specimens. These results are important for the current research of s trengthening processes in stage IV. (C) 1999 Acta Metallurgica Inc. Publish ed by Elsevier Science Ltd. All rights, reserved.