Effects of very high cycle fatigue (VHCF) damage were investigated in an austenitic-ferritic duplex stainless steel using the hard X-ray diffraction technique applying a beam diameter in the order of the mean grain size. Diffraction patterns were collected using a large 2D detector as function of the position along the load axis as well as perpendicular to the load axis of hourglass-shaped ultrasonic fatigue specimens. Intensities, angular positions and widths of Bragg reflections from individual grains were studied as a function of load cycles and stress amplitudes. Whereas rocking curves (RC) of ferrite grains behave nearly unaffected by the cyclic load, a splitting of RCs of austenite grains was observed and is taken as an indication for the VHCF damage. The frequency of split RCs of austenite grains increases with the number of load cycles and is found to be a function of the local stress amplitude. The latter one can be modeled by means of the finite element method (FEM). Taken from the 2Θ angles of Bragg peaks the internal compressive lattice strain of ferrite and austenite grains is found to be released for low but increases again for high numbers of load cycles. The evolution of lattice strain and the frequency of split RCs of austenite grains correlate with the appearance of slip bands at the sample surface seen by scanning electron microscopy (SEM) in combination with electron channeling contrast imaging (ECCI) and in the bulk verified by transmission electron microscopy (TEM). Microcrack formation in ferrite grains is assumed originated by the high density of slip bands in austenite grains generated by very high cycle fatigue.

X-ray scattering experiments on femtosecond laser-excited gold nanoparticle suspensions are presented. It is shown that the time-resolved pump-probe technique using the X-ray pulse structure at synchrotron sources is capable of resolving structural dynamics on the nanometer scale to high precision. The estimation of X-ray flux density allows the projection of experiments on an X-ray free-electron laser probing single nanoparticles in a one-shot exposure.

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Ultrafast time resolved x-ray powder scattering is used to reveal the structural dynamics in BaTiO3 powder excited by femtosecond laser pulses. The lattice excitation close to the Curie point of BaTiO3 is analyzed by refining the powder pattern (Rietveld method) to obtain the lattice state and the atomic positions. It is found that the tetragonal distortion of the ferroelectric phase is diminished within the 100ps time resolution of the experiment. The unit cell polarization, however, is not affected by this excitation, evidenced by the preserved Ti and oxygen displacement. The change in splitting relaxes on the nanosecond time scale.

The layout and the characteristics of the hard X-ray beamline BL10 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA are described. This beamline is equipped with a Si(111) channel-cut monochromator and is dedicated to X-ray studies in the spectral range from ∼4 keV to ∼16 keV photon energy. There are two different endstations available. While X-ray absorption studies in different detection modes (transmission, fluorescence, reflectivity) can be performed on a designated table, a six-axis kappa diffractometer is installed for X-ray scattering and reflectivity experiments. Different detector set-ups are integrated into the beamline control software, i.e. gas-filled ionization chambers, different photodiodes, as well as a Pilatus 2D-detector are permanently available. The performance of the beamline is illustrated by high-quality X-ray absorption spectra from several reference compounds. First applications include temperature-dependent EXAFS experiments from liquid-nitrogen temperature in a bath cryostat up to ∼660 K by using a dedicated furnace. Besides transmission measurements, fluorescence detection for dilute sample systems as well as surface-sensitive reflection-mode experiments are presented.