Revealing the intrinsic dislocation storage capability in nanocrystalline nickel

• Significant intragranular dislocation accumulation was observed in nanocrystalline Ni.
• Large plastic deformation produced high density of deformation twins.
• Dislocation accumulation was enabled primarily by dislocation–twin interactions.
• The intrinsic potential of nanocrystalline metals in dislocation storage was disclosed.

Lacking of dislocation storage capability has hitherto been considered an intrinsic feature for most nanocrystalline (NC) metals. Only under specific deformation conditions can trapped dislocations be detected inside the nano-grains, such as at liquid-nitrogen temperature or under complicated stress states. Here we show that, contrary to common belief, significant intragranular dislocation accumulation has been observed in NC Ni deformed under conventional uniaxial loading at room temperature. Considerable amount of deformation twins, which were progressively introduced during deformation, were identified to play a key role in pinning and stabilizing these dislocations. These observations disclose the intrinsic potential of NC metals in dislocation storage and may help with achieving high strength and acceptable ductility simultaneously in these materials.