Intra- versus intergranular strain partitioning and sub-grain orientation gradient at high temperature: strain rate effect on grain boundary

Advanced surface characterisation techniques were used to identify microplasticity at high temperature on a polycrystalline nickel-base superalloy at different strain rates. High resolution digital image correlation and laser confocal scanning microscopy aimed at detecting both displacement/height jumps due to discrete slip activity and surface slope due to crystal reorientation. Preliminary results demonstrated the role of the deformation rate on the strain partitioning at grain boundaries, twin boundaries and within grains. The goal of this proposal is to complement surface analyses with volumetric analyses to identify sub-surface onset of damage (cavitation, cracks, etc.) using a combination of diffraction contrast tomography for both grain orientation and morphology and phase contrast tomography for damage identification. Topotomography will document microplasticity in the volume. In-situ PCT and DCT testing will aim at correlating damage development to onset of microplasticity.