Realization of Al/High Strength Steel: Joints by Ultrasound Supported Friction Stir Welding - Process and Robustness, Mechanical Properties using Destructive and Non-Destructive Testing Methods, Microstructure, Corrosion, and Joining Area Integrated Corrosion Protection

• Applicants: Professor Dr.-Ing. Wolfram Fuerbeth; Professor Dr.-Ing. Guntram Wagner; Dr.-Ing. Bernd Wolter
• Subject Area: Production Automation and Assembly Technology
• Term: from 2012 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 228911405

The successful development and the construction of a completely new hybrid welding process, the Ultrasound Assisted Friction Stir Welding (UA-FSW), was in focus of the project, until now. It was found that the FSW process on the one hand is very suitable to produce material composites between dissimilar materials, even with very different melting points, and on the other hand that the parallel to the FSW process transmitted power ultrasound improves the monotonic and cyclic properties of the produced FSW-joints as expected. In recent years important developments in the FSW process technology as well as in the field of materials used in industrial application occur. New FSW tools with fixed shoulder and rotating pin make it possible to weld materials with very different melting points without an impermissibly wear of the FSW-tool. Furthermore, high-strength steels are increasingly being used in vehicle technology as elements of lightweight structures. However, attempts to produce Al / highstrength steel-joints by conventional FSW with sufficient strength were not successful. In this case, UA-FSW again is a pioneering joining process because the additional ultrasound can enable a more intensive joint between the materials without an increase of the temperature in the joining area or a higher wear of the FSW-tool. Therefore, Al / high-strength steel-joints should be produced in the third period by UA-FSW. Beside destructive testing methods, preprocess, in-line, and post-process non-destructive testing methods are provided. In addition, the microstructure of the produced joints will be analyzed and the corrosion behavior of the dissimilar joints will be investigated with a special focus on integrated corrosion protection concepts. The use of thermographic methods to optimize the joining process has proven itself and will be continued. The Al-lightweight materials EN-AW 6061 and EN-AC 48000 considered in the own project and other projects of the SPP1640 during the first two funding periods will be reused. As high strength steel joining partners boronalloyed tempered steel 22MnB5 in the martensitic condition, DP600 and MS-W 1200 should be considered, which are gaining more and more significance in industrial applications. Furthermore, the results will be compared with the joints between Al-alloys and the low strength steels C45 and DC04 of the second founding period.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1640: Joining by Plastic Deformation