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

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.

SUBMITTER: Zhang Z 

PROVIDER: S-EPMC4682111 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature