X-ray imaging of cast microstructure by using ultra-bright synchrotron radiation

Feasibility examinations on phase (refraction) contrast X-ray imaging with highly brilliant microbeam were carried out on metallic materials containing crack, slit or second particle by using the branched experimental hutch C of beamline BL24XU, SPring-8. Two kinds of X-ray beam conditions were adopted. One was direct monochrome beam tuned at 15 keV. The other was the refracted X-ray beam which was expanded horizontally by asymmetric reflections for the monochrome beam. Vertical expansion was also obtained by synchronized stage scanning to enlarge the area of observation. We examined wedge shape specimens of SUS316 steel with a fatigue crack, 5N-aluminum with slits and nodular iron, respectively. The phase contrast profile of both the fatigue crack in SUS316 and slits fabricated in aluminum was extracted from recorded image by subtracting absorption contrast. The slit-depth was successfully evaluated by the relation of the distance between highlight and dark bands to the incident angle. For nodular iron, the phase contrast profile of the spheroidal graphite was detected together with the absorption contrast. (author)