Strain tensor tomography with X-ray powder diffraction

Material properties of poly-crystalline engineering materials such as fatigue strength or corrosion resistance are linked to local strain and residual stress distributions. Accordingly, accurate strain measurements on micrometer scales provide the basis for reliable life time and failure predictions. Up to now, there are two X-ray methods available for depth-resolved strain measurements - both utilizing challenging setups and suffer from anisotropic gauge volumes. Inspired by a previously developed theoretical frame work, we propose the utilization of a pencil beam and X-ray powder diffraction for the tomographic reconstruction of local strain distributions achieving an aspect ratio of 1:1. A test scan at PETRA III showed encouraging results, but reconstruction quality was severely affected by anisotropic diffraction caused by an undersized beam. At ID11, we will use larger beams to collect signal from more grains and avoid corresponding artifacts.