Abstract
Damage tolerance can be an elusive characteristic of structural materials requiring both high
strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of
interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile
strength levels ofB1GPa, excellent ductility (B60–70%) and exceptional fracture toughness
(KJIc4200MPaOm). Here through the use of in situ straining in an aberration-corrected
transmission electron microscope, we report on the salient atomistic to micro-scale
mechanisms underlying the origin of these properties. We identify a synergy of multiple
deformation mechanisms, rarely achieved in metallic alloys, which generates high strength,
work hardening and ductility, including the easy motion of Shockley partials, their interactions
to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated
dislocations. We further show that crack propagation is impeded by twinned, nanoscale
bridges that form between the near-tip crack faces and delay fracture by shielding the
crack tip.
