Fatigue Properties of 6061-T6 Aluminum Alloy T-Joints Processed by Vacuum Brazing and TIG Welding

Abstract

The increasing use of aluminum alloys in transportation including railways, shipbuilding and aeronautics demands more efficient and reliable welding processes, which requires sufficient understanding of fatigue failure. Tungsten inert gas (TIG) welding and vacuum brazing (VB) T-joints of AlMgSi alloy 6061 in the artificially aged condition T6 were studied. This work focuses on the contrasting difference of fatigue behavior of T-joints made from both the traditional process of TIG welding, and the emerging process of vacuum brazing. The fatigue properties of AA 6061-T6 welding under constant amplitude (CA) and variable amplitude (VA) loading were studied. The aim of the CA part in this paper was to identify the differences between brazing and welding on fatigue performance and size effect. The fatigue experiments of TIG welding and vacuum brazing in 6061-T6 aluminum alloys were performed to investigate fatigue strengths. The test results were compared with the results suggested by the International Institute of Welding (IIW), British Standard (BS) and Eurocode 9 recommendations. Meanwhile, in terms of size effect, the thickness correction exponents were compared with the thickness correction exponents suggested by the IIW. The VA part of the work was examined to identify the effects of the mean stress which might increase fatigue lives less than predicted by linear damage summation models. The effects of the mean stress in different correction methods were evaluated.