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Surface characterization and influence of anodizing process on fatigue life of Al 7050 alloy

Shahzad, Majid and Chaussumier, Michel and Chieragatti, Rémy and Mabru, Catherine and Rezaï-Aria, Farhad Surface characterization and influence of anodizing process on fatigue life of Al 7050 alloy. (2011) Materials & Design, 32 (6). 3328-3335 . ISSN 0261-3069

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Official URL: http://dx.doi.org/10.1016/j.matdes.2011.02.027


The present study investigates the influence of anodizing process on fatigue life of aluminium alloy 7050-T7451 by performing axial fatigue tests at stress ratio ‘R’ of 0.1. Effects of pre-treatments like degreasing and pickling employed prior to anodizing on fatigue life were studied. The post-exposure surface observations were made by scanning electron microscope (SEM) to characterize the effect of each treatment before fatigue testing. The surface observations have revealed that degreasing did not change the surface topography while pickling solution resulted in the formation of pits at the surface. Energy dispersive spectroscopy (EDS) was used to identify those constituent particles which were responsible for the pits formation. These pits are of primary concern with respect to accelerated fatigue crack initiation and subsequent anodic coating formation. The fatigue test results have shown that pickling process was detrimental in reducing the fatigue life significantly while less decrease has been observed for anodized specimens. Analyses of fracture surfaces of pickled specimens have revealed that the process completely changed the crack initiation mechanisms as compared to non-treated specimens and the crack initiation started at the pits. For most of the anodized specimens, fatigue cracks still initiated at the pits with very few cracks initiated from anodic coating. The decrease in fatigue life for pickled and anodized 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 pickled and anodized specimens as compare to bare specimens tested at same stress levels.

Item Type:Article
HAL Id:hal-01666700
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Université de Toulouse > Ecole nationale supérieure des Mines d'Albi-Carmaux - IMT Mines Albi (FRANCE)
Université de Toulouse > Institut National des Sciences Appliquées de Toulouse - INSA (FRANCE)
Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Laboratory name:
Institut Clément Ader - ICA (Toulouse, France) - Surfaces, Usinage, Matériaux et Outillages - Fatigue, Modélisation, Endommagement et Usure
Département de Mécanique des Structures et Matériaux - DMSM (Toulouse, France)
Deposited On:19 Sep 2011 09:03

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