Relationships between welding parameters, aging conditions, and weld properties in AA7075-T6 friction stir welds
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ORIGINAL ARTICLE
Relationships between welding parameters, aging conditions, and weld properties in AA7075-T6 friction stir welds D. Ambrosio1
· C. Garnier1 · V. Wagner1 · E. Aldanondo2 · G. Dessein1 · O. Cahuc3
Received: 10 July 2020 / Accepted: 25 September 2020 / Published online: 11 October 2020 © Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract The influence of processing parameters and several combinations of natural as well as artificial aging on the mechanical properties of friction stir welded AA7075-T6 is analyzed in the present investigation. Different sets of welding parameters were employed to obtain joints characterized by different peak temperatures and thermal cycles. The joint obtained with the highest welding speed has guaranteed the best mechanical properties. The latter were shown to be strongly correlated to heat input, which influences both densities of dislocations in nugget zone grains and growth and dissolution of strengthening precipitates in the heat-affected zone that establish the mechanical characteristics of friction stir welds. On the other hand, artificial aging has drastically reduced the strain at break due to strain localization in the heat affected zones while it has proved its effectiveness in stabilizing the mechanical properties when exposed to further natural aging at room temperature. Keywords Friction stir welding · Aluminum alloys · Mechanical properties · Natural aging · Artificial aging
1 Introduction Friction stir welding is a solid-state joining process extensively studied in the last three decades [1]. Over the years, several studies have focused on the aging of friction stir welds made with precipitation hardening aluminum alloys to study the evolution of the mechanical properties as a function of various heat treatments. The need arises from the fact that, although FSW joints have mechanical properties far superior to those obtained by other techniques [2], there are heat-affected zones that weaken the joint due to heating and cooling cycles [3]. However, the mechanical behavior of friction stir welds age-hardenable aluminum alloys is strongly influenced by the time elapsed after welding due to their dependence on natural aging [4]. Thus, it is necessary to identify suitable post-welding procedures D. Ambrosio
[email protected] 1
Laboratoire G´enie de Production (LPG), INP/ENIT 65016, Tarbes, France
2
LORTEK Technological Centre, Basque Research and Technology Alliance (BRTA), Arranomendia Kalea 4A, 20240, Ordizia, Spain
3
Institute of mechanics and engineering (I2M), CNRS, University of Bordeaux, 33400, Talence, France
to obtain high strength and stable properties in FSW joints to facilitate the implementation of the FSW process for manufacturing aerospace structures [5]. In early studies, Mahoney et al. [6] demonstrated that post-welding artificial aging (AA) does not affect the yield strength but decreases ductility and ultimate tensile strength in FSW AA7075-T6 joints. For the same material, Fuller et al. [7] reported the evolution
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