Nondestructive 3-Dimensional X-ray Diffraction Tomography of Stress/StrainDistribution around Fatigue Cracks in Al-Li 2090

摘要

Sychrotron X-ray microbeams were used to characterize the three-dimensionaldistribution of macrotexture associated with asperity formation during fatigue crack propagation in Al-Li 2090 T8E41. Nondestructive techniques were developed, and beams formed by a 10 micrometers diameter collimator were applied. Focus was on the center portion of 12.5mm thick plates where macrotexture correlates with asperity geometry. A very distinct type of mesotexture was found: multiple adjacent grains have nearly identical orientations and form substantial volumes of near-single-crystal (NSC) material. Transitions between differently oriented NSC volumes or an NSC region and more randomly oriented grains seem to bound asperities.