Micro-strains in cold rolled Cu-Nb nanolayered composites determined by X-ray line profile analysis

X-ray line profile analysis was used to investigate micro-strains in sputter-deposited Cu-Nb nanolayered composites, with individual layer thickness of 75 nm, in the as-deposited and cold rolled conditions. The measured anisotropic line broadening in these strongly textured foils was interpreted in terms of dislocations. A very high dislocation density, of the order of 10^16 m^-2, was inferred from the X-ray data in the as-deposited foil. No significant change in dislocation density was noted after cold rolling to around 150% elongation in the rolling direction. Furthermore, the preferred orientation of the Burgers vectors, both before and after rolling, for the majority of the dislocations was parallel to the interface. The apparent lack of dislocation storage beyond the initial density after large plastic strains is discussed in terms of dislocation mechanisms.