Displacement measurements from nanoprecipitates in alloyed Cu single crystals using anomalous small- and wide-angle X-ray scattering

Single crystals of Cu-3Ti, Cu-41.5Ni-16Fe and Cu-23Ni-7Fe (at. %) were studied by anomalous small-angle and wide-angle X-ray scattering in order to determine the displacements induced by the precipitates (ordered Cu₄Ti rods in the first case or (Ni,Fe) discs in the other cases) as a function of ageing time and temperature. The small-angle scattering patterns give information on the size and arrangement of the precipitates, while the scattering around the Bragg peak allows the elastic lattice distortions around these precipitates to be determined. The precipitates formed in these three alloys are elastically contracted while the matrix enriched in Cu atoms is dilated. This succession of compressed and dilated regions is responsible for the alignment of the precipitates along the elastically soft directions <100>.