Interaction between strain localization and crack initiation in an IN718 polycrystal after stress-assisted grain boundary cracking: multimod

We aim to combine 2D surface (SEM) and 3D bulk observations (synchrotron) in order to study the initial stages of damage in IN718 samples under Stress Assisted Grain Boundary Oxidation (SAGBO) conditions. Prior to the experiment, two miniature tensile samples will be deformed at 650 C at two strain rates until appearance of strain localization and first cracks, detected by Laser Confocal Scanning Microscopy, EBSD and DIC. The samples will then be investigated by a combination of X-ray diffraction imaging techniques: (i) phase and diffraction contrast tomography (visualization of cracks and surrounding 3D grain micro-structure), (ii) Topotomography of grains near crack initiation sites (3D visualization of strain localization) and (iii) scanning 3DXRD (elastic strain state of the in selected regions of interest). After the characterization at room temperature, the progressive evolution of SAGBO damage will be followed by means of in-situ phase contrast tomography (see MA5180).