Planar slip-driven fatigue crack initiation and propagation in an equiatomic CrMnFeCoNi high-entropy alloy

High-cycle fatigue crack initiation and propagation in an equiatomic CrMnFeCoNi high-entropy alloy were investigated using smooth specimens. The microstructural deformation characteristics, i.e., planar dislocation slip, significantly affected the fatigue crack initiation and small fatigue crack propagation. The deformation localization associated with dislocation planarity led to multiple crack initiation on the slip planes. The crack propagation mechanism comprised crack formation on slip planes around the main crack tip and subsequent coalescence. The fatigue crack propagation mechanism shifted to Mode I type as the crack length increased.