X-ray line-broadening study of the dislocation cell structure in deformed [001]-orientated copper single crystals

Abstract

Copper single crystals of [001] orientation were deformed plastically in tension to different stress levels. Using a double-crystal diffractometer with self-compensation of wave-length dispersion and practically negligible instrumental line-broadening, the {002} Bragg reflections were investigated. The broadened diffraction profiles of the deformed crystals were markedly asymmetric and could be resolved into two well-behaved (symmetrical) sub-profiles. The latter could be assigned in a straight-forward manner to the alternating regions of high and low local dislocation density, i.e. to the cell walls and to the cell interiors. The analysis of the sub-profiles permitted the determination of the local dislocation densities and the description of the local dislocation arrangements in terms of a parameter which characterizes the screening of the strain fields of neighbouring dislocations. It is found, in conformity with transmission electron microscopy (TEM) observations, that the character of the overall dislocation distribution varies with increasing deformation and that the principle of similitude is not obeyed. From the X-ray line-broadening data overall dislocation densities were obtained which agree well with values obtained by other authors using TEM. The results of the present study are discussed and compared with published work based mainly on TEM and on measurements of stored energy.