Application of Diffraction-Amalgamated Grain Boundary Tracking (DAGT) to Fatigue Crack Propagation Behavior in High Strength Aluminum Alloy

The fatigue crack propagation behavior in an Al-Zn-Mg-Cu alloy was investigated by amalgamating X-ray diffraction (XRD) with grain boundary tracking (GBT). The integrated technique, Diffraction-Amalgamated Grain Boundary Tracking (DAGT), provides new possibilities for mapping grain morphologies and crystallographic orientations in three-dimension (3D). 3D crack morphologies at different propagation stages in the bulk of metallic materials were successfully obtained by using Synchrotron Radiation X-ray Microtomography (SRCT). Using 2D slices of the 3D crack, the crack length increment was measured to calculate the crack growth rate which varies significantly. Typical crack morphology, such as crack tilt, is detected by the observation of 2D tomographic slice image. The observed interaction between fatigue crack and polycrystalline microstructures can be analyzed in 3D. Through this synthesis of techniques, DAGT, a detailed direct assessment of microstructure and crack propagation behaviors has been achieved.