Microstructure mapping of a friction stir welded AA2050 Al–Li–Cu in the T8 state

Abstract

The heterogeneous precipitate microstructure of a AA2050 Al–Li–Cu in the T8 state after friction stir welding has been mapped by small-angle X-ray scattering (SAXS). 2D resolved maps of the fraction and size of both T₁ platelets precipitates and clusters/GP zones formed at room temperature are provided. TEM micrographs of selected zone confirm the interpretation of SAXS intensities. This microstructure mapping is compared to microhardness mapping and a direct correlation is shown. Short duration heat treatments made in a salt bath help understanding precipitate stability and suggest that the temperature exploration alone explains to a large extent the distribution of the precipitates microstructure across the welded structure.

Keywords:

• precipitation
• FSW
• SAXS
• Al–Cu–Li alloys

Acknowledgements

This work was financially supported by the ANR MatetPro program (ANR-08-MAPR-0020-05 “CORALIS”). The authors would like to thank the staff at D2AM-BM02 CRG beamline at ESRF.