Synchrotron X-Ray Radiation and Deformation Studies

In the present thesis two different synchrotron X-ray diffraction techniques capable of producing non-destructive information from the bulk of samples, have been investigated. Traditionally depth resolu-tion in diffraction experiments is obtained by inserting pinholes in both the incoming and diffracted beam.

For materials science investigations of local strain and texture properties this leads to very slow data acquisition rates, especially when characterisation is performed on the level of the individual grains. To circumvent this problem a conical slit was manufactured by wire electrodischarge machining.

The conical slit has six 25µm thick conically shaped openings matching six of the Debye-Scherrer cones from a fcc powder. By combining the conical slit with a micro-focused incoming beam of hard X-rays an embedded gauge volume is defined. Using a 2D detector, fast and complete information can be ob-tained regarding the texture and strain properties of the material within this particular gauge volume.

The capacity of the conical slit for depth profiling is demonstrated by scanning the gauge volume within the bulk of a polycrystalline copper sample, obtaining a two-dimensional map of the grain boundary morphology. Another X-ray diffraction technique was applied on the three-dimensional X-ray diffraction (3DXRD) microscope at the ESRF synchrotron.

The microscope uses a new technique based on ray tracing of diffracted high energy X-rays, providing a fast and non-destructive scheme for mapping the embedded grains within thick samples in three dimensions. All essential features like the position, volume, orien-tation, stress-state of individual grains can be determined, including the morphology of the grain boundaries.

The first results obtained by using the novel tracking technique are presented in this thesis. For valida-tion, the tracking technique has been applied just below a sample surface and the tracking results are compared to electron microscopy investigations of the same sample surface. The positions of the grain boundaries were reconstructed from the tracking data with an average uncertainty of 26µm and the grain orientations were calculated with a precision of 0.1°.

The tracking technique was applied in a preliminary experiment with the intention of following the rotation history of the crystal lattices in individual grains during deformation. The tracking technique was furthermore applied in combination with synchrotron X-ray tomography in order to gain new in-formation on the wetting kinetics of liquid gallium in aluminium grain boundaries.

Finally, an electron microscopy investigation was carried out in order to describe the lattice rotations and texture evolution in uniaxially compressed aluminium single crystals and polycrystals.