Quantifying microscale drivers for fatigue failure via coupled synchrotron X-ray characterization and simulations
Sven E. Gustafson, Wolfgang Ludwig, Paul A. Shade, Diwakar Naragani, Darren C. Pagan, Phil Cook, Can Yildirim, C. Detlefs, Michael D. Sangid
Abstract
During cyclic loading, localization of intragranular deformation due to crystallographic slip acts as a precursor for crack initiation, often at coherent twin boundaries. A suite of high-resolution synchrotron X-ray characterizations, coupled with a crystal plasticity simulation, was conducted on a polycrystalline nickel-based superalloy microstructure near a parent-twin boundary in order to understand the deformation localization behavior of this critical, 3D microstructural configuration. Dark-field X-ray microscopy was spatially linked to high energy X-ray diffraction microscopy and X-ray diffraction contrast tomography in order to quantify, with cutting-edge resolution, an intragranular misorientation and high elastic strain gradients near a twin boundary. These observations quantify the extreme sub-grain scale stress gradients present in polycrystalline microstructures, which often lead to fatigue failure.