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Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

  • Author(s): Zhang, ZJ
  • Mao, MM
  • Wang, J
  • Gludovatz, B
  • Zhang, Z
  • Mao, SX
  • George, EP
  • Yu, Q
  • Ritchie, RO
  • et al.
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 of ∼1 GPa, excellent ductility (∼60-70%) and exceptional fracture toughness (KJIc>200 MPa √m). 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.

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