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Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy

Micro-shot peening under two Almen intensities was performed to increase the fatigue endurance limit of anodized AA 7075 alloy in T6 condition. Compressive residual stress (CRS) and a nano-grained structure were present in the outermost as-peened layer. Microcracks in the anodized layer obviously ab...

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Autores principales: Su, Chih-Hang, Chen, Tai-Cheng, Ding, Yi-Shiun, Lu, Guan-Xun, Tsay, Leu-Wen
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9920401/
https://www.ncbi.nlm.nih.gov/pubmed/36770165
http://dx.doi.org/10.3390/ma16031160
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author Su, Chih-Hang
Chen, Tai-Cheng
Ding, Yi-Shiun
Lu, Guan-Xun
Tsay, Leu-Wen
author_facet Su, Chih-Hang
Chen, Tai-Cheng
Ding, Yi-Shiun
Lu, Guan-Xun
Tsay, Leu-Wen
author_sort Su, Chih-Hang
collection PubMed
description Micro-shot peening under two Almen intensities was performed to increase the fatigue endurance limit of anodized AA 7075 alloy in T6 condition. Compressive residual stress (CRS) and a nano-grained structure were present in the outermost as-peened layer. Microcracks in the anodized layer obviously abbreviated the fatigue strength/life of the substrate. The endurance limit of the anodized AA 7075 was lowered to less than 200 MPa. By contrast, micro-shot peening increased the endurance limit of the anodized AA 7075 to above that of the substrate (about 300 MPa). Without anodization, the fatigue strength of the high peened (HP) specimen fluctuated; this was the result of high surface roughness of the specimen, as compared to that of the low peened (LP) one. Pickling before anodizing was found to erode the outermost peened layer, which caused a decrease in the positive effect of peening. After anodization, the HP sample had a greater fatigue strength/endurance limit than that of the LP one. The fracture appearance of an anodized fatigued sample showed an observable ring of brittle fracture. Fatigue cracks present in the brittle coating propagated directly into the substrate, significantly damaging the fatigue performance of the anodized sample. The CRS and the nano-grained structure beneath the anodized layer accounted for a noticeable increase in resistance to fatigue failure of the anodized micro-shot peened specimen.
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spelling pubmed-99204012023-02-12 Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy Su, Chih-Hang Chen, Tai-Cheng Ding, Yi-Shiun Lu, Guan-Xun Tsay, Leu-Wen Materials (Basel) Article Micro-shot peening under two Almen intensities was performed to increase the fatigue endurance limit of anodized AA 7075 alloy in T6 condition. Compressive residual stress (CRS) and a nano-grained structure were present in the outermost as-peened layer. Microcracks in the anodized layer obviously abbreviated the fatigue strength/life of the substrate. The endurance limit of the anodized AA 7075 was lowered to less than 200 MPa. By contrast, micro-shot peening increased the endurance limit of the anodized AA 7075 to above that of the substrate (about 300 MPa). Without anodization, the fatigue strength of the high peened (HP) specimen fluctuated; this was the result of high surface roughness of the specimen, as compared to that of the low peened (LP) one. Pickling before anodizing was found to erode the outermost peened layer, which caused a decrease in the positive effect of peening. After anodization, the HP sample had a greater fatigue strength/endurance limit than that of the LP one. The fracture appearance of an anodized fatigued sample showed an observable ring of brittle fracture. Fatigue cracks present in the brittle coating propagated directly into the substrate, significantly damaging the fatigue performance of the anodized sample. The CRS and the nano-grained structure beneath the anodized layer accounted for a noticeable increase in resistance to fatigue failure of the anodized micro-shot peened specimen. MDPI 2023-01-29 /pmc/articles/PMC9920401/ /pubmed/36770165 http://dx.doi.org/10.3390/ma16031160 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Su, Chih-Hang
Chen, Tai-Cheng
Ding, Yi-Shiun
Lu, Guan-Xun
Tsay, Leu-Wen
Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy
title Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy
title_full Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy
title_fullStr Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy
title_full_unstemmed Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy
title_short Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy
title_sort effects of micro-shot peening on the fatigue strength of anodized 7075-t6 alloy
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9920401/
https://www.ncbi.nlm.nih.gov/pubmed/36770165
http://dx.doi.org/10.3390/ma16031160
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