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An investigation of the stored energy and thermal stability in a Cu-Ni-Si alloy processed by high-pressure torsion

An investigation of the stored energy and thermal stability in a Cu-Ni-Si alloy processed by high-pressure torsion
An investigation of the stored energy and thermal stability in a Cu-Ni-Si alloy processed by high-pressure torsion
In the present study, the stored energy and activation energy for recrystallization were investigated for a Cu–Ni–Si alloy after high-pressure torsion processing for N = ½, 1, 5 and 10 turns at room temperature. The contributions of geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs) and vacancies to the stored energy were calculated through the Vickers microhardness measurements, kernel average misorientation (KAM) measurements and an analysis by differential scanning calorimetry (DSC). The results show that the total stored energy decreases rapidly after equivalent strain of εeq ~ 9 (N = 1 turn) and then saturates through εeq ~ 86 (N = 10 HPT turns) at ~70 J/mol. Concurrently, the local stored energy in GNDs and SSDs was found to depend strongly on the radial distance from the centre of the disc and increase with increasing equivalent strain at εeq ~ 16 and saturate with further straining. Accordingly, the results indicate that the GNDs and vacancies are responsible for the high stored energy in the initial stage of deformation at equivalent strain range of εeq = 8.6–16 (N = ½–1 turn) and thereafter their contribution decreases slightly due to the occurrence of dynamic recrystallization and the formation of fine grains. At the same time, the contribution of the SSDs is similar to that of the GNDs only in high strain deformation as at εeq = 49.3 (N = 5 turns) to accommodate the deformation process. The recrystallization peak was detected in the range of 157–194 °C depending on the number of HPT turns and heating rate. An activation energy for recrystallization was estimated in the range of ~ 89.7–98.7 kJ/mol, thereby suggesting a poor thermal stability.
Copper alloy, DSC, hardness, recrystallization, severe plastic deformation, stored energy
0141-8610
688-712
Azzeddine, Hiba
f32633f8-2f8a-433e-9180-ada2b8704eae
Bourezg, Yousf Islem
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Khereddine, Adbel Yazid
efcb32e2-ee8d-44fd-b624-d13d61dfa63f
Baudin, Thierry
933b263a-4a22-4c65-9599-16b27346e946
Helbert, Anne-Laure
0fe1fd69-b89f-4b5c-a14a-71cd7cf63f10
Brisset, François
c93ca177-5b75-400d-a9fb-85a567cebec6
Kawasaki, Megumi
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Bradai, Djamel
59c22bbc-952f-4ab9-8619-8d63d6ee8a19
Langdon, Terence G
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Azzeddine, Hiba
f32633f8-2f8a-433e-9180-ada2b8704eae
Bourezg, Yousf Islem
aab04bbc-d0f1-4ef4-8bef-2471dbbca4f0
Khereddine, Adbel Yazid
efcb32e2-ee8d-44fd-b624-d13d61dfa63f
Baudin, Thierry
933b263a-4a22-4c65-9599-16b27346e946
Helbert, Anne-Laure
0fe1fd69-b89f-4b5c-a14a-71cd7cf63f10
Brisset, François
c93ca177-5b75-400d-a9fb-85a567cebec6
Kawasaki, Megumi
944ba471-eb78-46db-bfb7-3f0296d9ef6d
Bradai, Djamel
59c22bbc-952f-4ab9-8619-8d63d6ee8a19
Langdon, Terence G
86e69b4f-e16d-4830-bf8a-5a9c11f0de86

Azzeddine, Hiba, Bourezg, Yousf Islem, Khereddine, Adbel Yazid, Baudin, Thierry, Helbert, Anne-Laure, Brisset, François, Kawasaki, Megumi, Bradai, Djamel and Langdon, Terence G (2020) An investigation of the stored energy and thermal stability in a Cu-Ni-Si alloy processed by high-pressure torsion. Philosophical Magazine, 100 (6), 688-712. (doi:10.1080/14786435.2019.1703055).

Record type: Article

Abstract

In the present study, the stored energy and activation energy for recrystallization were investigated for a Cu–Ni–Si alloy after high-pressure torsion processing for N = ½, 1, 5 and 10 turns at room temperature. The contributions of geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs) and vacancies to the stored energy were calculated through the Vickers microhardness measurements, kernel average misorientation (KAM) measurements and an analysis by differential scanning calorimetry (DSC). The results show that the total stored energy decreases rapidly after equivalent strain of εeq ~ 9 (N = 1 turn) and then saturates through εeq ~ 86 (N = 10 HPT turns) at ~70 J/mol. Concurrently, the local stored energy in GNDs and SSDs was found to depend strongly on the radial distance from the centre of the disc and increase with increasing equivalent strain at εeq ~ 16 and saturate with further straining. Accordingly, the results indicate that the GNDs and vacancies are responsible for the high stored energy in the initial stage of deformation at equivalent strain range of εeq = 8.6–16 (N = ½–1 turn) and thereafter their contribution decreases slightly due to the occurrence of dynamic recrystallization and the formation of fine grains. At the same time, the contribution of the SSDs is similar to that of the GNDs only in high strain deformation as at εeq = 49.3 (N = 5 turns) to accommodate the deformation process. The recrystallization peak was detected in the range of 157–194 °C depending on the number of HPT turns and heating rate. An activation energy for recrystallization was estimated in the range of ~ 89.7–98.7 kJ/mol, thereby suggesting a poor thermal stability.

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Hiba-PM-CuNiSi - Accepted Manuscript
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Accepted/In Press date: 6 December 2019
e-pub ahead of print date: 20 December 2019
Published date: 18 March 2020
Keywords: Copper alloy, DSC, hardness, recrystallization, severe plastic deformation, stored energy

Identifiers

Local EPrints ID: 436580
URI: http://eprints.soton.ac.uk/id/eprint/436580
ISSN: 0141-8610
PURE UUID: 3492a887-3e2e-4c5b-a2dd-bdadfe7b8331
ORCID for Terence G Langdon: ORCID iD orcid.org/0000-0003-3541-9250

Catalogue record

Date deposited: 16 Dec 2019 17:30
Last modified: 26 Nov 2021 07:14

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Contributors

Author: Hiba Azzeddine
Author: Yousf Islem Bourezg
Author: Adbel Yazid Khereddine
Author: Thierry Baudin
Author: Anne-Laure Helbert
Author: François Brisset
Author: Megumi Kawasaki
Author: Djamel Bradai

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