Internal stress measurements by high-energy synchrotron X-ray diffraction at increased specimen-detector distance

High-energy X-ray diffraction has recently been shown to be a viable technique to measure volume-averaged lattice strains in the bulk of metallic polycrystals at increased speed compared to neutron diffraction. The established procedure is to irradiate the sample under investigation with monochromatic X-rays (similar to100 keV) and to record complete diffraction rings with an area detector. The lattice strains are obtained by analyzing the minute distortions of these rings. In the present paper we present first results obtained using a setup in which two area detectors are positioned at a large distance (7 m) from the specimen. Although only segments of the rings can be recorded this way, this approach offers a number of advantages. In situ tensile tests were performed on a gamma-TiAl-based alloy as an example to demonstrate the potential of the method. Both materials science aspects as well as consequences for further method development will be discussed. (C) 2002 Elsevier Science B.V. All rights reserved.