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Nanomechanical behavior and structural stability of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion

Nanomechanical behavior and structural stability of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion
Nanomechanical behavior and structural stability of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion
A CoCrFeNiMn high-entropy alloy (HEA), in the form of a face-centered cubic (fcc) solid solution, was processed by high-pressure torsion (HPT) to produce a nanocrystalline (nc) HEA. Significant grain refinement was achieved from the very early stage of HPT through 1/4 turn and an nc structure with an average grain size of ?40 nm was successfully attained after 2 turns. The feasibility of significant microstructural changes was attributed to the occurrence of accelerated atomic diffusivity under the torsional stress during HPT. Nanoindentation experiments showed that the hardness increased significantly in the nc HEA during HPT processing and this was associated with additional grain refinement. The estimated values of the strain-rate sensitivity were maintained reasonably constant from the as-cast condition to the nc alloy after HPT through 2 turns, thereby demonstrating a preservation of plasticity in the HEA. In addition, a calculation of the activation volume suggested that the grain boundaries play an important role in the plastic deformation of the nc HEA where the flow mechanism is consistent with other nc metals. Transmission electron microscopy showed that, unlike conventional fcc nc metals, the nc HEA exhibits excellent microstructural stability under severe stress conditions.
high-entropy alloys, high-pressure torsion, nanocrystalline metal, nanoindentation
2804-2815
Lee, Dong-Hyun
ed19915c-a04e-468e-9246-7cd76b9c590c
Choi, In-Chul
7a33a581-e44b-4f53-8ded-5e46af6f5506
Seok, Moo-Young
f772e8bf-0d95-4f93-b0c2-f2a665a91f8e
He, Junyang
cafc9d17-af90-4f09-8988-61c9ccb9b6bb
Lu, Zhaoping
33e0322f-c987-46e1-a857-6ed7b7275241
Suh, Jin-Yoo
4bd2e7c3-b427-4f29-bb30-f7726d33253f
Kawasaki, Megumi
944ba471-eb78-46db-bfb7-3f0296d9ef6d
Langdon, T
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Jang, Jae-il
c8160c1e-ce1b-4518-8a52-930cb9f54800
Lee, Dong-Hyun
ed19915c-a04e-468e-9246-7cd76b9c590c
Choi, In-Chul
7a33a581-e44b-4f53-8ded-5e46af6f5506
Seok, Moo-Young
f772e8bf-0d95-4f93-b0c2-f2a665a91f8e
He, Junyang
cafc9d17-af90-4f09-8988-61c9ccb9b6bb
Lu, Zhaoping
33e0322f-c987-46e1-a857-6ed7b7275241
Suh, Jin-Yoo
4bd2e7c3-b427-4f29-bb30-f7726d33253f
Kawasaki, Megumi
944ba471-eb78-46db-bfb7-3f0296d9ef6d
Langdon, T
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Jang, Jae-il
c8160c1e-ce1b-4518-8a52-930cb9f54800

Lee, Dong-Hyun, Choi, In-Chul, Seok, Moo-Young, He, Junyang, Lu, Zhaoping, Suh, Jin-Yoo, Kawasaki, Megumi, Langdon, T and Jang, Jae-il (2015) Nanomechanical behavior and structural stability of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion. Journal of Materials Research, 30 (18), 2804-2815. (doi:10.1557/jmr.2015.239).

Record type: Article

Abstract

A CoCrFeNiMn high-entropy alloy (HEA), in the form of a face-centered cubic (fcc) solid solution, was processed by high-pressure torsion (HPT) to produce a nanocrystalline (nc) HEA. Significant grain refinement was achieved from the very early stage of HPT through 1/4 turn and an nc structure with an average grain size of ?40 nm was successfully attained after 2 turns. The feasibility of significant microstructural changes was attributed to the occurrence of accelerated atomic diffusivity under the torsional stress during HPT. Nanoindentation experiments showed that the hardness increased significantly in the nc HEA during HPT processing and this was associated with additional grain refinement. The estimated values of the strain-rate sensitivity were maintained reasonably constant from the as-cast condition to the nc alloy after HPT through 2 turns, thereby demonstrating a preservation of plasticity in the HEA. In addition, a calculation of the activation volume suggested that the grain boundaries play an important role in the plastic deformation of the nc HEA where the flow mechanism is consistent with other nc metals. Transmission electron microscopy showed that, unlike conventional fcc nc metals, the nc HEA exhibits excellent microstructural stability under severe stress conditions.

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More information

Accepted/In Press date: 24 July 2015
Published date: 18 August 2015
Keywords: high-entropy alloys, high-pressure torsion, nanocrystalline metal, nanoindentation
Organisations: Energy Technology Group, Engineering Science Unit, Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 386313
URI: http://eprints.soton.ac.uk/id/eprint/386313
PURE UUID: 77b4e8bf-05b5-4914-9532-5b6609972c0f
ORCID for T Langdon: ORCID iD orcid.org/0000-0003-3541-9250

Catalogue record

Date deposited: 29 Jan 2016 16:53
Last modified: 10 Dec 2019 01:47

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