Data and code from: Multiscale fatigue crack initiation in hierarchical additively manufactured alloys

Bio-inspired hierarchical microstructures offer a route towards engineered
fatigue resistance in additively manufactured alloys. However, it remains
unclear how discrete structural constituents independently govern damage
accumulation, particularly during the critical fatigue initiation regime
where short cracks strongly interact with local microstructure. Here, we
investigate multiscale fatigue initiation in a dual-phase, nanolamellar
AlCoCrFeNi2.1 high-entropy alloy. By comparing microscale specimens that
isolate the nanolamellar structure against macroscale specimens containing
the full melt-pool architecture, we identify size-dependent fatigue
initiation mechanisms. We find that failure is dictated by nanolamellar
interfaces at the microscale, whereas mesoscale melt pool boundaries serve
to initiate fatigue at the macroscale. This mechanistic shift is
accompanied by a transition from macroscale quasi-brittle failure to
microscale plasticity-driven crack extension. Our results provide a
physical framework for understanding how structural hierarchy governs the
transition from discrete microstructural deformation to continuum fatigue
fracture behavior, informing the design of damage-tolerant, additively
manufactured alloys.