Abstract: The present study investigates the unique dislocation structures in Ni-10Cr alloy after fatigue loading, focusing on the role of short-range ordering (SRO) in modifying slip behavior. Although Ni-10 at.%Cr alloy processes a high stacking fault energy (SFE), the careful observation of fatigue microstructures reveals complex dislocation structures where planar slip bands coexist with wavy-slip dislocation structures like veins and labyrinths, indicating a deviation from the conventional wavy-slip dislocation structures expected in high SFE metals. The development of interpenetrating wavy/planar-slip fatigue dislocation structures exhibits a strong dependence on accumulated plastic strain, i.e., from low-density planar slip bands at early stages, to scattered cross-slip activation at intermediate cycles, and eventually to stable wavy-planar coexistence at higher cycles (2000-20,000 cycles). Scanning transmission electron microscopy imaging and two-beam diffraction analysis reveal that the planar slip bands are confined to {111} planes with a narrow spacing (∼80 nm), attributed to the SRO-induced suppression of cross-slip via glide plane softening. Notably, this hybrid fatigue dislocation structure still remains partially intact after subsequently monotonic tensile loading, particularly at 2000 cycles, correlating with an enhanced mechanical performance. These findings highlight the non-classical deformation response of high-SFE alloys and underscore the sustained yet evolving influence of SRO on the fatigue behavior, offering insights into the design of fatigue-resistant FCC alloys.

Key words: Ni-10 at.%Cr alloy, Fatigue, High stacking fault energy, Short-range ordering, Interpenetrating wavy/planar-slip dislocation structure