Application of energy-dispersive diffraction to the analysis of multiaxial residual stress fields in the intermediate zone between surface and volume

The non-destructive and phase selective analysis of residual stresses caused by material processing in polycrystalline samples is usually performed by diffraction methods. Using X-ray and neutron probes, respectively, complementary information on the residual stress distribution in the nearest surface region and the volume of the material is available. However, there remains a gap with respect to the accessible near surface zone, which concerns a range between about 10 μm and 1 mm, where the conventional X-ray methods are no longer and the neutron methods are not yet sensitive. In order to extend the information depth to this 'intermediate' zone between the surface and the volume, use can be made of energy-dispersive (ED) diffraction in reflection geometry with photon energies up to about 100 keV. Measuring and evaluation procedures applied so far in the well-established X-ray stress analysis by means of angle-dispersive (AD) diffraction were adapted to the ED case and further developed using the advantages provided by ED diffraction. By simulations and experimental examples, the multitude of reflections recorded simultaneously in one diffracted energy spectrum will be shown to be the decisive additional parameter, which can be used for a self-consistent depth resolved triaxial residual stress gradient analysis