Direct observation of strain in bulk subgrains and dislocation walls by high angular resolution three-dimensional X-ray diffraction

The X-ray diffraction (XRD) method “high angular resolution 3DXRD” is briefly introduced, and results are presented for a single bulk grain in a polycrystalline copper sample deformed in tension. It is found that the three-dimensional reciprocal-space intensity distribution of a 400 reflection associated with the grain, shows a distinct structure consisting of sharp bright peaks superimposed on a cloud of enhanced intensity. The bright peaks (which arise from individual subgrains) are found to be subjected to backward strain (on average) while the fraction of the material giving rise to the cloud of enhanced intensity is subjected to forward strain. Based on the latter observation the, originally tentative, interpretation of the cloud as arising from dislocation walls is substantiated.