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Realization of ultrasound enhanced friction stir welded Al/Mg- and Al/steel-joints

Process and robustness, mechanical and corrosion properties
: Thomä, Marco; Wagner, Guntram; Straß, Benjamin; Conrad, Christian; Wolter, Bernd; Benfer, Sigrid; Fürbeth, Wolfram


Hovanski, Y.:
Friction stir welding and processing IX : 26.02.-02.03.2017, San Diego, California
Cham: Springer International Publishing, 2017 (The minerals, metals & materials series)
ISBN: 978-3-319-52382-8 (Print)
ISBN: 978-3-319-52383-5 (Online)
Symposium on Friction Stir Welding and Processing (FSW/P) <9, 2017, San Diego/Calif.>
Deutsche Forschungsgemeinschaft DFG
SPP 1640; Joining by Plastic Deformation
Conference Paper
Fraunhofer IZFP ()
friction stir welding; ultrasound enhancement; Dissimilar metals; nondestructive testing; corrosion

As an innovative hybrid joining process ultrasound enhanced friction stir welding (USE-FSW) was successfully applied on Al/Mg-joints and offers a beneficial impact on the resulting microstructure and mechanical properties. Whereas in conventional FSW of Al to Mg continuous band-shaped intermetallic layers of Al3Mg2 and Mg17Al12 are always present, the formation of these layers can be influenced positively by the ultrasound energy that is transferred into the stirred zone in USE-FSW. In this case, the intermetallic phases are spread over the complete nugget zone. Consequently, the tensile strength increases about 25% and the fatigue strength rises by up to 3.5 times. Based on this USE-FSW was investigated with regard to possible advantages for Al/steel-hybrid-joints. Preliminary investigations have shown significant differences in the microstructure of ultrasound enhanced and non-ultrasound enhanced EN AW-6061/DC04-joints. While conventional FSW led to hooks and larger particles of steel in the aluminum, USE-FSW-joints show remarkably smaller and more homogenous distributed steel particles in the nugget. Beside mechanical investigations, non-destructive examinations and corrosion tests were carried out.