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Aerospace components undergo a series of manufacturing process steps where a possible alteration of the mechanical performance and conformance of a given part can happen – in a desirable or unfavorable way. In this work, extensive studies have been performed to deepen the understanding on the impact of the friction stir welding process on Aluminium-based alloys, yet the impact of the process on the material is not fully understood. Better understanding is based on improved analytical capabilities allowing for a deeper understanding around this material and its processing.
This work utilizes state-of-the-art experimental techniques at different length scales to reveal the impact of the manufacturing process on Aluminium 2099. First, Scanning Electron Microscopy (SEM), Electron Back-Scattered Diffraction (EBSD) and Energy Dispersive X-Ray Spectroscopy (EDS) is performed to reveal the microstructural morphology at micro and macro-levels.
Focused Ion Beam SEM (FIB-SEM) and coupled Transmission Electron Microscopy (TEM)-EDS was necessary to reveal the changes in dislocations and precipitate structures within three zones: base metal, heat affected zone and weld metal, where the latter suffered from lower hardness and strength.
TEM-EDS analysis clearly reveals the nano-structural changes related to the welding process, but it is unable to confirm the presence of Lithium in this alloy. In a next step Atom Probe Tomography (APT) was used to reveal the chemistries and structures which contain Lithium at the nanoscale.
The combination of a multitude of analytical techniques at different length-scales was necessary to characterize the impact of the welding on the material. Clearly, analytical techniques at a macro- and micro-scale alone are not able to answer the questions regarding the material modification caused by the friction stir welding process. The combination of TEM/EDS and APT provides more clear evidence and answers.