Achieving ultra-high strength of Al-Cu-Li alloys by the combination of high pressure torsion and age-hardening
Achieving ultra-high strength of Al-Cu-Li alloys by the combination of high pressure torsion and age-hardening
The combined strengthening effects of high pressure torsion (HPT) and age hardening on a recently developed 3rd generation Al-Cu-Li alloy was investigated. Solution treated samples were processed through HPT at room temperature, followed by low temperature artificial ageing (i.e. T4-HPT-AA). A micro-hardness of ∼ 240 Hv was achieved on ageing at 110 oC/60h after HPT. A further improvement in the hardness to ∼ 260 Hv was accomplished by a pre-ageing 110 oC/24h before HPT combined with a post-HPT ageing process at 110 oC for 180h (i.e. T6-HPT-AA). These novel multi-stage processes give rise to an increase in hardness by a factor of 2 as compared to the T4 condition (∼ 120 Hv). After HPT the grain size was dramatically refined to the ultrafine-grained (UFG) structure, accompanied by a large amount of dislocations. No long-range ordered precipitates were observed after HPT and subsequent ageing treatments. Instead, atom probe tomography (APT) provided clear evidence that Cu-Mg co-clusters were homogeneously distributed in the matrix of T4 and T6 processed samples and they segregate strongly to the grain boundaries (GBs) during HPT. Further ageing treatment after HPT leads to the segregation of clusters to dislocations. A strengthening model that incorporates dislocation hardening, grain boundary hardening, solid solution strengthening and a new short-range order strengthening mechanisms was used to predict the yield strength of the alloy. This model indicates that the combined effect due to all three types of Cu-Mg clusters (clustering in matrix, clustering at GBs and at dislocations) is dominant for the strength in all conditions.
Dong, Jiahui
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Gao, Nong
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Chen, Ying
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Cao, Lingfei
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Song, Hui
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Fröck, Hannes
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Milkereit, Benjamin
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Starink, Marco J.
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14 January 2022
Dong, Jiahui
8c20a76c-8541-463e-977b-de0aa381f7ee
Gao, Nong
9c1370f7-f4a9-4109-8a3a-4089b3baec21
Chen, Ying
7c5ac05a-9540-4fe2-bb6e-aee7fa104929
Cao, Lingfei
2c426a4b-0eaa-4283-bd45-c0002e915ccb
Song, Hui
a48e8327-5a8e-4e05-9f37-7ec14f95f1c3
Fröck, Hannes
4d55ebbf-afca-4913-8cdd-68c4b618b730
Milkereit, Benjamin
7fc4cf93-212a-4ba1-86d6-69934b194499
Starink, Marco J.
fe61a323-4e0c-49c7-91f0-4450e1ec1e51
Dong, Jiahui, Gao, Nong, Chen, Ying, Cao, Lingfei, Song, Hui, Fröck, Hannes, Milkereit, Benjamin and Starink, Marco J.
(2022)
Achieving ultra-high strength of Al-Cu-Li alloys by the combination of high pressure torsion and age-hardening.
Materials Science And Engineering A, 832, [142504].
(doi:10.1016/j.msea.2021.142504).
Abstract
The combined strengthening effects of high pressure torsion (HPT) and age hardening on a recently developed 3rd generation Al-Cu-Li alloy was investigated. Solution treated samples were processed through HPT at room temperature, followed by low temperature artificial ageing (i.e. T4-HPT-AA). A micro-hardness of ∼ 240 Hv was achieved on ageing at 110 oC/60h after HPT. A further improvement in the hardness to ∼ 260 Hv was accomplished by a pre-ageing 110 oC/24h before HPT combined with a post-HPT ageing process at 110 oC for 180h (i.e. T6-HPT-AA). These novel multi-stage processes give rise to an increase in hardness by a factor of 2 as compared to the T4 condition (∼ 120 Hv). After HPT the grain size was dramatically refined to the ultrafine-grained (UFG) structure, accompanied by a large amount of dislocations. No long-range ordered precipitates were observed after HPT and subsequent ageing treatments. Instead, atom probe tomography (APT) provided clear evidence that Cu-Mg co-clusters were homogeneously distributed in the matrix of T4 and T6 processed samples and they segregate strongly to the grain boundaries (GBs) during HPT. Further ageing treatment after HPT leads to the segregation of clusters to dislocations. A strengthening model that incorporates dislocation hardening, grain boundary hardening, solid solution strengthening and a new short-range order strengthening mechanisms was used to predict the yield strength of the alloy. This model indicates that the combined effect due to all three types of Cu-Mg clusters (clustering in matrix, clustering at GBs and at dislocations) is dominant for the strength in all conditions.
Text
2-J Dong Materials Scie Eng A Vol 832 2022
- Accepted Manuscript
More information
Accepted/In Press date: 10 December 2021
e-pub ahead of print date: 11 December 2021
Published date: 14 January 2022
Additional Information:
Funding Information:
This work was financially supported by the Faculty of Engineering and the Environment at the University of Southampton . In addition, we gratefully acknowledge the experimental support of TEM from the Xiamen University of Technology , China, APT provided by the Electron Microscopy Centre of Chongqing University and financially supported by the National Natural Science Foundation of China ( 51871033 ). Also appreciate the University of Rostock, Germany, for assistance in DSC experiments.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Identifiers
Local EPrints ID: 482956
URI: http://eprints.soton.ac.uk/id/eprint/482956
ISSN: 0921-5093
PURE UUID: 9b35c87a-f642-4b25-804c-6f57b215eaee
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Date deposited: 17 Oct 2023 16:56
Last modified: 18 Mar 2024 05:28
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Contributors
Author:
Jiahui Dong
Author:
Ying Chen
Author:
Lingfei Cao
Author:
Hui Song
Author:
Hannes Fröck
Author:
Benjamin Milkereit
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