Micro-Strain and Cyclic Slip Accumulation in a Polycrystalline Nickel-Based Superalloy

This work provides a comprehensive characterization and analysis of deformation and fatigue damage mechanisms
in a nickel-based superalloy during ambient temperature fatigue and points to a fundamental deformation mechanism
that results in the onset of crack nucleation. Strain and slip irreversibility are investigated at the nanometer scale us-
ing high-resolution digital image correlation and high-resolution electron backscatter diffraction, highlighting distinct
deformation mechanisms contributing to crack nucleation. It is observed during early fatigue cycling at relatively
low applied stress, the formation of intense slip events that induce grain boundary shearing. This results in intense
micro-scale strain in the neighboring grains, producing localized plasticity and stresses. Such stresses facilitate fatigue
extrusion-intrusion mechanisms during subsequent cycling, resulting in preferred crack nucleation. Finally, the config-
urations within the microstructure that promote such deformation and damage mechanisms sequence are highlighted