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Effect of annealing on mechanical properties of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion

Effect of annealing on mechanical properties of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion
Effect of annealing on mechanical properties of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion
A CoCrFeNiMn high-entropy alloy (HEA) was processed by high-pressure torsion (HPT) under 6.0 GPa pressure up to 10 turns at room temperature. It is shown that there is a gradual evolution in hardness with increasing numbers of turns but full homogeneity is not achieved even after 10 turns. Microhardness measurements reveal that the material reaches a saturation hardness value of ~4.41 GPa and in this condition the microstructure shows exceptional grain refinement with a grain size of ~10 nm. An ultimate strength value of ~1.75 GPa and an elongation to fracture of ~4% were obtained in a sample processed for 5 turns. The nanostructured HEA was subjected to post-deformation annealing (PDA) at 473-1173 K and it is shown that the hardness increases slightly to 773 K due to precipitation and then decreases up to 1173 K due to a combination of recrystallization, grain growth and a dissolution of the precipitates. The formation of brittle precipitates, especially ?-phase, at 873 and 973 K significantly reduces the ductility. Short-term annealing for 10 min at 1073 K prevents grain growth and leads to a combination of high strength and good ductility including an ultimate tensile strength of ~830 MPa and an elongation to failure of ~65%.
0921-5093
294-303
Shahmir, Hamed
9d330616-d35d-4db0-96e8-26195ae1c511
He, Junyang
cafc9d17-af90-4f09-8988-61c9ccb9b6bb
Lu, Zhaoping
33e0322f-c987-46e1-a857-6ed7b7275241
Kawasaki, Megumi
944ba471-eb78-46db-bfb7-3f0296d9ef6d
Langdon, Terence G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Shahmir, Hamed
9d330616-d35d-4db0-96e8-26195ae1c511
He, Junyang
cafc9d17-af90-4f09-8988-61c9ccb9b6bb
Lu, Zhaoping
33e0322f-c987-46e1-a857-6ed7b7275241
Kawasaki, Megumi
944ba471-eb78-46db-bfb7-3f0296d9ef6d
Langdon, Terence G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86

Shahmir, Hamed, He, Junyang, Lu, Zhaoping, Kawasaki, Megumi and Langdon, Terence G. (2016) Effect of annealing on mechanical properties of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion. Materials Science and Engineering: A, 676, 294-303. (doi:10.1016/j.msea.2016.08.118).

Record type: Article

Abstract

A CoCrFeNiMn high-entropy alloy (HEA) was processed by high-pressure torsion (HPT) under 6.0 GPa pressure up to 10 turns at room temperature. It is shown that there is a gradual evolution in hardness with increasing numbers of turns but full homogeneity is not achieved even after 10 turns. Microhardness measurements reveal that the material reaches a saturation hardness value of ~4.41 GPa and in this condition the microstructure shows exceptional grain refinement with a grain size of ~10 nm. An ultimate strength value of ~1.75 GPa and an elongation to fracture of ~4% were obtained in a sample processed for 5 turns. The nanostructured HEA was subjected to post-deformation annealing (PDA) at 473-1173 K and it is shown that the hardness increases slightly to 773 K due to precipitation and then decreases up to 1173 K due to a combination of recrystallization, grain growth and a dissolution of the precipitates. The formation of brittle precipitates, especially ?-phase, at 873 and 973 K significantly reduces the ductility. Short-term annealing for 10 min at 1073 K prevents grain growth and leads to a combination of high strength and good ductility including an ultimate tensile strength of ~830 MPa and an elongation to failure of ~65%.

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Accepted/In Press date: 30 August 2016
e-pub ahead of print date: 31 August 2016
Published date: 31 October 2016
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 399928
URI: http://eprints.soton.ac.uk/id/eprint/399928
ISSN: 0921-5093
PURE UUID: 473e3387-6594-4790-9892-3f008aea170e
ORCID for Terence G. Langdon: ORCID iD orcid.org/0000-0003-3541-9250

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Date deposited: 05 Sep 2016 12:38
Last modified: 15 Mar 2024 05:52

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Contributors

Author: Hamed Shahmir
Author: Junyang He
Author: Zhaoping Lu
Author: Megumi Kawasaki

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