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Corrosion and stress corrosion cracking behaviour of 2050 aluminium-lithium alloy joined by friction stir welding (FSW)

Proton, Vincent and Alexis, Joël and Andrieu, Eric and Odemer, Grégory and Blanc, Christine and Delfosse, Jérôme Corrosion and stress corrosion cracking behaviour of 2050 aluminium-lithium alloy joined by friction stir welding (FSW). (2012) In: EUROCORR 2012, 9 September 2012 - 13 September 2012 (Istanbul, Turkey).

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Abstract

The present work deals with the influence of an external mechanical stress on the corrosion behaviour of a Friction Sir Welding butt joint. In order to understand the corrosion behaviour of the whole welded joint, some zones have been removed and studied individually. A welded joint was obtained by joining together two plate of aluminium-lithium alloy 2050-T3 and then has been submitted to an additional T8 post-welding heat treat-ment. Actually a typical friction stir weld consists of the unaffected base material (BM), a heat affected zone (HAZ), a thermo-mechanically affected zone (TMAZ) and a dynamically recrystallized zone (nugget). Some samples were removed from the BM and the nugget of the welded joint in or-der to study the corrosion and stress corrosion cracking behaviour of these two zones individually. Immersion tests with and without an external mechanical stress were performed in a 0.7 M NaCl solution to study the corrosion behaviour of the two zones and the influence of the stress. For both kinds of experiments, the corrosion damage was determined by measuring the average depth and the maximal depth of the corrosion defects. The results showed that the two zones presented different corrosion morphologies. The BM exhibited susceptibility to intragranular corrosion while the nugget presented both intragranular and intergranular corrosion. The external mechanical stress did not modify the corrosion morphologies and the open circuit potential. Nevertheless, as they present different corrosion morphologies, the external mechanical stress did not have the same influence on the propagation of the corrosion damage. Indeed, the external mechanical stress did not promote the propagation of the corrosion in the BM whereas it does in the Nugget. Considering the whole welded joint, the corrosion morphologies of the BM and the nugget were the same than those observed for each zone considered individually. A previous work [1] has shown that galvanic coupling phenomena existed between the different parts of the welded joint and the BM acted as a sacrificial anode. As the external stress did not change the OCP of the different parts, no modification of the galvanic coupling phenomena was expected and the BM was found to be more damaged than the other zones.

Item Type:Conference or Workshop Item (Paper)
Audience (conference):International conference proceedings
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > European Aeronautic Defence and Space company - EADS (FRANCE)
Laboratory name:
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Deposited By: Joël ALEXIS
Deposited On:16 Jan 2014 14:22

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