Thick 7XXX friction stir welds resistant to coarse recrystallization during solution heat treatments
(2020) ICAA 2020: 17th International conference on aluminium alloys — Location: Grenoble (online) (26.October.2020)
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- Abstract
- Friction stir welding (FSW) of 7XXX aluminium alloy series is becoming an essential technique in industrial applications. However, FSW welds are weaker than the T6 parent material. Softening of the welds is observed due to dissipated heat during welding. Optimum T6 mechanical strength after welding can be recovered by a dedicated treatment. This treatment is composed of two-steps heating: solution heat treatment, typically at 470°C for 30 minutes plus quench, then artificial aging at 120°C for 24 hours. However, significant grain coarsening in the weld nugget zone (NZ) takes place. This is known as secondary recrystallization phenomenon, sometimes leading to abnormal grain growth (AGG). Recrystallization of NZ is detrimental for mechanical properties. This work is highlighting a processing route to avoid secondary recrystallization in FSWed joints. It is realised by controlling thermal cycle during welding and post-weld heat treatments, opening the path to excellent welds presenting the strength of the T6 base material as well as ductility.
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Citations
Lezaack, M. B., & Simar, A. (2020). Thick 7XXX friction stir welds resistant to coarse recrystallization during solution heat treatments. ICAA 2020: 17th International conference on aluminium alloys, Grenoble (online). https://hdl.handle.net/2078.5/268929