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Effect of ablative and non-ablative Laser Shock Peening on AA7075-T651 corrosion and fatigue performance

Effect of ablative and non-ablative Laser Shock Peening on AA7075-T651 corrosion and fatigue performance
Effect of ablative and non-ablative Laser Shock Peening on AA7075-T651 corrosion and fatigue performance
The fatigue performance from pre-corroded pits was studied for laser shock peening of aluminium alloy AA7075-T651 (UNS A97075) with and without a protective ablation layer. Surface and microstructural characterisation showed laser shock peening generated high residual stress fields of up to –400 MPa, limited hardness increase, and moderate surface roughness increase. The laser shock peened specimens were exposed to 3.5 wt.% sodium chloride solution for different levels of galvanostatic control. The compressive residual stresses did not significantly affect the corrosion behaviour, corrosion pit morphology or pit depth. Laser-shock-peening-induced surface roughness was shown to have the most detrimental impact on corrosion performance. Fatigue testing of pre-corroded AA7075-T651 showed pits act as stress concentrations, causing cracks to initiate shortly after dynamic loading, and causing a reduction of at least 50% of its fatigue life. The laser shock peening markedly increased fatigue life, by up to 400% compared to corroded untreated AA7075-T651, due to the residual stresses effectively counteracting the stress concentrations produced by these pits. Laser shock peened AA7075-T651, that suffers subsequent pitting corrosion, can be expected to still have fatigue performance and a lifetime equivalent or better than uncorroded unpenened AA7075-T651.
0267-0836
Sanchez Araujo, Alvaro, Gonzalo
cd16af17-6f1b-491d-a671-b49e5451d37d
Leering, Mitchell
aa9c75e2-76c9-4f8e-badd-66e2bee32b70
Glaser, Daniel
e7df12ab-5bf8-46de-9c63-18973fd8c2e1
Fitzpatrick, M.E.
26eb385f-4b65-4f9c-86fc-6c2464f9fc1e
Wharton, Julian
965a38fd-d2bc-4a19-a08c-2d4e036aa96b
Reed, Philippa
8b79d87f-3288-4167-bcfc-c1de4b93ce17
Sanchez Araujo, Alvaro, Gonzalo
cd16af17-6f1b-491d-a671-b49e5451d37d
Leering, Mitchell
aa9c75e2-76c9-4f8e-badd-66e2bee32b70
Glaser, Daniel
e7df12ab-5bf8-46de-9c63-18973fd8c2e1
Fitzpatrick, M.E.
26eb385f-4b65-4f9c-86fc-6c2464f9fc1e
Wharton, Julian
965a38fd-d2bc-4a19-a08c-2d4e036aa96b
Reed, Philippa
8b79d87f-3288-4167-bcfc-c1de4b93ce17

Sanchez Araujo, Alvaro, Gonzalo, Leering, Mitchell, Glaser, Daniel, Fitzpatrick, M.E., Wharton, Julian and Reed, Philippa (2021) Effect of ablative and non-ablative Laser Shock Peening on AA7075-T651 corrosion and fatigue performance. Materials Science and Technology. (In Press)

Record type: Article

Abstract

The fatigue performance from pre-corroded pits was studied for laser shock peening of aluminium alloy AA7075-T651 (UNS A97075) with and without a protective ablation layer. Surface and microstructural characterisation showed laser shock peening generated high residual stress fields of up to –400 MPa, limited hardness increase, and moderate surface roughness increase. The laser shock peened specimens were exposed to 3.5 wt.% sodium chloride solution for different levels of galvanostatic control. The compressive residual stresses did not significantly affect the corrosion behaviour, corrosion pit morphology or pit depth. Laser-shock-peening-induced surface roughness was shown to have the most detrimental impact on corrosion performance. Fatigue testing of pre-corroded AA7075-T651 showed pits act as stress concentrations, causing cracks to initiate shortly after dynamic loading, and causing a reduction of at least 50% of its fatigue life. The laser shock peening markedly increased fatigue life, by up to 400% compared to corroded untreated AA7075-T651, due to the residual stresses effectively counteracting the stress concentrations produced by these pits. Laser shock peened AA7075-T651, that suffers subsequent pitting corrosion, can be expected to still have fatigue performance and a lifetime equivalent or better than uncorroded unpenened AA7075-T651.

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More information

Submitted date: 1 February 2021
Accepted/In Press date: 1 July 2021

Identifiers

Local EPrints ID: 450629
URI: http://eprints.soton.ac.uk/id/eprint/450629
ISSN: 0267-0836
PURE UUID: e776c3ce-c703-46e3-b45f-7bcf82b5488e
ORCID for Alvaro, Gonzalo Sanchez Araujo: ORCID iD orcid.org/0000-0002-7246-7000
ORCID for Julian Wharton: ORCID iD orcid.org/0000-0002-3439-017X
ORCID for Philippa Reed: ORCID iD orcid.org/0000-0002-2258-0347

Catalogue record

Date deposited: 05 Aug 2021 16:31
Last modified: 06 Aug 2021 01:48

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Contributors

Author: Alvaro, Gonzalo Sanchez Araujo ORCID iD
Author: Mitchell Leering
Author: Daniel Glaser
Author: M.E. Fitzpatrick
Author: Julian Wharton ORCID iD
Author: Philippa Reed ORCID iD

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