Anisotropy of partial structure factors in an unmixed Cu-Ni-Fe single crystal studied by anomalous small-angle X-ray scattering

To study the anisotropy of phase separation in Cu-Ni-Fe alloys, small-angle X-ray scattering has been performed on a single-crystal foil. The 3D scattering pattern consists of an orientation-dependent ring. The intensity is a maximum along the (100)* and a minimum along the (111)* directions. The scattering is explained in terms of a non-interacting pile-up model of alternating Cu- and Ni-Fe-rich platelets along (100) directions. Moreover, the magnitude of the anomalous effect depends on the crystallographic orientation. The analysis shows that the two-phase description is insufficient to describe the derived PSFS. An interpretation is offered in terms of an interfacial segregation of Fe with a maximum amplitude in the plane of the (100) platelets.