Title: Exceptional fracture toughness of CrCoNi-based medium- and high-entropy alloys at 20 kelvin

Abstract

Medium- and high-entropy alloys based on the CrCoNi-system have been shown to display outstanding strength, tensile ductility and fracture toughness (damage-tolerance properties), especially at cryogenic temperatures. Here we examine the J_Ic and (back-calculated) K_JIc fracture toughness values of the face-centered cubic, equiatomic CrCoNi and CrMnFeCoNi alloys at 20 K. At flow stress values of ~1.5 GPa, crack-initiation K_JIc toughnesses were found to be exceptionally high, respectively 235 and 415 MPa√m for CrMnFeCoNi and CrCoNi, with the latter displaying a crack-growth toughness K_ss exceeding 540 MPa√m after 2.25 mm of stable cracking, which to our knowledge is the highest such value ever reported. Characterization of the crack-tip regions in CrCoNi by scanning electron and transmission electron microscopy reveal deformation structures at 20 K that are quite distinct from those at higher temperatures and involve heterogeneous nucleation, but restricted growth, of stacking faults and fine nanotwins, together with transformation to the hexagonal closed-packed phase. The coherent interfaces of these features can promote both the arrest and transmission of dislocations to generate respectively strength and ductility which strongly contributes to sustained strain hardening. Indeed, we believe that these nominally single-phase, concentrated solid-solution alloys develop their fracture resistance through a progressive synergy of deformationmore » mechanisms, including dislocation glide, stacking-fault formation, nano-twinning and eventually in situ phase transformation, all of which serve to extend continuous strain hardening which simultaneously elevates strength and ductility (by delaying plastic instability), leading to truly exceptional resistance to fracture.« less

Authors:

Liu, Dong  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-5947-8362"

Yu, Qin  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-5099-0327"

Kabra, Saurabh  ^[3];

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Jiang, Ming  ^[1];

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Forna-Kreutzer, Paul  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-5934-9432"

Zhang, Ruopeng  ^[4];

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Payne, Madelyn  ^[4];

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Walsh, Flynn  ^[5];

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Gludovatz, Bernd  ^[6];

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Asta, Mark  ^[5];

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Minor, Andrew M.  ^[4];

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• Search DOE PAGES for ORCID "0000-0003-3606-8309"

George, Easo P. ^[7]; Ritchie, Robert O.  ^[5]

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• Search DOE PAGES for ORCID "0000-0002-0501-6998"

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+ Show Author Affiliations

1. Univ. of Bristol (United Kingdom)
2. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
3. Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL)
4. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Molecular Foundry
5. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
6. Univ. of New South Wales, Sydney, NSW (Australia)
7. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Ruhr Univ., Bochum (Germany)

Publication Date:

Fri Dec 02 00:00:00 EST 2022

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); UK Engineering and Physical Sciences Research Council

OSTI Identifier:

1986007

Grant/Contract Number:  

AC02-05CH11231; EP/N004493/2; EP/T000368/1

Resource Type:

Accepted Manuscript

Journal Name:

Science

Additional Journal Information:

Journal Volume: 378; Journal Issue: 6623; Journal ID: ISSN 0036-8075

Publisher:

AAAS

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE