Modelling the influence grain misorientations have on fatigue behaviour
of Ni-based DS superalloys: State-of-the-art
Abstract
Influence grain miss-orientations have on mechanical behaviour of
Ni-based DS superalloys was investigated using crystal plasticity finite
element modelling, in this review. Loading axes aligned with
solidification direction, in both low-cycle-fatigue (LCF) and
fatigue-crack-growth (FCG) behaviour, were considered. Influences of
grain miss-orientations were investigated based on FE-modelling using
actual microstructures measured with EBSD. Since the FE-modelling was
able to simulate full history of fatigue stress-strain responses, under
LCF loading, it was employed to explain heterogeneous deformation and
localised high-stresses (dependent on grain-sizes and miss-orientations)
linked to shorter LCF-life in test data that validated the FE-model. The
model was then used to study FCG behaviour by considering crack-tip
deformation under fatigue loading. Since FCG was exclusively due to
mechanical deformation, it was sufficient to use accumulated plastic
strain as a damage criterion, in XFEM. Results revealed a high
dependency on grain-orientation.