Thermo-mechanical fatigue behavior and crystal plasticity modelling of
an additively manufactured nickel-based superalloy
Abstract
Thermo-mechanical fatigue (TMF) tests were performed for vertically and
horizontally selective-laser-melting (SLM) additively manufactured
nickel-based superalloy, and also wrought superalloy for comparison. A
mechanical strain amplitude of 0.8% was applied over a temperature
range of 350-650℃. SLM samples in different printing directions exhibit
notable disparities in cyclic hardening and softening, as well as
average stress behaviour. Horizontally printed samples exhibit superior
fatigue life under out-of-phase (OP) conditions compared to in-phase
(IP) conditions. Compared to wrought samples, additively manufactured
samples exhibit longer lifetimes under both IP and OP TMF conditions,
but exhibit weaker performance during isothermal fatigue testing.
Meanwhile, SEM analysis indicates that defects between layers have a
greater impact on lifespan than intralayer defects. EBSD analysis
reveals the crucial influence of microstructure on the fatigue
performance of the samples. Despite having higher residual stress,
horizontally printed samples exhibit longer fatigue life due to their
finer grain size. The crystal plasticity finite element (CPFE) model was
established to simulate the TMF cyclic deformation behaviour. The
asymmetry of cyclic response was well captured, as well as the
hardening-softening behaviour. Furthermore, thermo-mechanical loading
was applied to a 2D model directly generated from EBSD based on this
model.