Effect of anodised coatings on fatigue crack growth rates in aluminium alloy

Cree, Alistair; Weidmann, G. W.

doi:10.1179/sur.1997.13.1.51

Cited by 23 publications

(9 citation statements)

References 3 publications

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“…Camargo et al [9] have shown that internal tensile residual stresses, as a consequence of anodization on 7050-T7451, is one of the reasons for degrading stress-life fatigue performance of the substrate. Study by Cree and Weidmann [10] on anodized 2024 alloy has demonstrated that fatigue crack growth rate can be significantly enhanced in the presence of thin anodic film. They explained the increased growth rate in terms of possible tensile residual stress in film and its inherent higher modulus.…”

Section: Introductionmentioning

confidence: 99%

Effect of sealed anodic film on fatigue performance of 2214-T6 aluminum alloy

Shahzad

Chaussumier

Chieragatti

et al. 2012

Surface and Coatings Technology

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The aim of present study is to investigate the influence of anodic film, grown by sulfuric acid anodizing and sealed in nickel-acetate solution, on fatigue strength of aluminum alloy 2214-T6 by conducting axial fatigue tests at stress ratio 'R' of 0.1 and − 1. The influence of sealed anodic film is to degrade the stress-life (S-N) fatigue performance of the base material at all stress levels. Effects of pre-treatments like degreasing and pickling employed prior to anodizing were also studied and no influence of these pre-treatments was observed on fatigue life. The surface and cross-section observations of anodic film were made by scanning electron microscope (SEM) before and after fatigue tests. The surface observations have revealed cavities which resulted from dissolution of coarse Al 2 Cu particles during anodization and network of micro-cracks on anodic film surface which were initiated as a result of sealing process. Some of these micro-cracks were found to penetrate up-to substrate and have detrimental effect on subsequent fatigue strength. The decrease in fatigue life for anodized-sealed specimens as compared to bare condition has been attributed to decrease in initiation period and multi-site crack initiations. Multi-site crack initiation has resulted in rougher fractured surfaces for the anodized specimens as compared to bare specimens tested at same stress levels.

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Section: Introductionmentioning

confidence: 99%

Effect of sealed anodic film on fatigue performance of 2214-T6 aluminum alloy

Shahzad

Chaussumier

Chieragatti

et al. 2012

Surface and Coatings Technology

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“…Anodizing is well-known electrolytic process that produces controlled columnar growth of amorphous aluminium oxide on the surface of aluminium alloys as documented in ASM Handbook (1998). Despite the benefits obtained by anodizing in terms of cor-rosion resistance, it has been shown (Cree and Weidmann, 1997) and (ESDU document 87026, 1994) that anodizing has adverse effect on fatigue life of aluminium alloys. It is generally accepted that this reduction in fatigue life is directly attributed to the brittle and porous nature of oxide layer and tensile residual stress induced during anodizing process as demonstrated by Camargo and Voorwald (2007) for alloy 7050-T7451 and Cirik and Genel (2008) for alloy 7075-T6.…”

Section: Introductionmentioning

confidence: 99%

Influence of surface treatments on fatigue life of Al 7010 alloy

Shahzad

Chaussumier

Chieragatti

et al. 2010

Journal of Materials Processing Technology

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OATAO is an open access repository that co llects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author -deposited version published in: http://oatao. The objective of the present work is to show the influence of machining and anodizing processes on fatigue life of alloy 7010-T7451. Two different cutting conditions were employed to obtain two different initial surface roughnesses. Degreasing, pickling and anodizing were then carried out. In the as machined condition, surface roughness is clearly effective in reducing fatigue life in this material. As the surface roughness increases fatigue life decreases and this effect is found to be more pronounced in high cycle fatigue where major portion of fatigue life is consumed in nucleating the cracks. Effects of pre-treatments, like degreasing and pickling employed prior to anodizing, on fatigue life of the given alloy were also studied. Fatigue curves showed that pickling had negative impact on fatigue life of specimens while degreasing showed no change in fatigue life. The small decrease in fatigue life of anodized specimens as compare to pickled specimens is attributed to brittle nature and micro-cracking of the coating. Scanning electron microscopic (SEM) examination revealed multi-site crack initiation for the pickled and anodized specimens. SEM examination also showed that pickling process attacked the grain boundaries and the inclusions present on the surface resulting in pits formation. These pits are of primary concern with respect to accelerated fatigue crack nucleation and subsequent anodized coating formation.

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“…According to Lockheed Martin surface treatment methods [8], the sulfuric acid process Type II had been used for the anodized materials being investigated in this study. Unfortunately, sulfuric acid anodizing has been reported to be more detrimental than the chromic acid process in terms of fatigue performance [16].…”

Section: Discussionmentioning

confidence: 99%

“…Cladding and anodizing have previously been observed to have deleterious effects on fatigue performance [16,17]. A clad layer has a much lower yield stress than the substrate material.…”

Section: Discussionmentioning

confidence: 99%