Combined micro-beam Laue and white beam topography: mapping local lattice orientation and misorientation

Abstract

Micro-beam Laue diffraction is a well-established technique to determine lattice orientation and lattice structure. A polychromatic X-ray beam is used to illuminate a scattering volume within individual crystallites. The resulting diffraction pattern consists of a number of Laue spots. By refinement of the exact spot positions, lattice orientation and deviatoric elastic strain of the single crystalline scattering volume can be determined. Diffraction spot shape is linked to the orientation spread in the scattering volume arising due to the local dislocation structure. However, angular resolution of Laue diffraction spots is limited due to small sample-to-detector distance (~100 mm) and large Laue camera pixel size (~40 µm). In contrast, X-ray diffraction topography allows high-resolution imaging of an individual reflection from a crystal. On beamline B16 at the Diamond Light Source, we have combined micro-beam Laue diffraction with simultaneous collection of diffraction topographs, using a second high-resolution X-ray camera in the far field. In situ deformation of a single grain within a thin Ni foil has been studied using this setup. While detailed analysis is ongoing, some early results are presented here to allow an assessment of the technique's utility and future development possibilities.