Lightweight and resilient components are the result of a newly developed process from the Materials Testing Institute at the University of Stuttgart. The researchers have developed a process based on friction stir welding that can be used to produce hybrid sheet metal blanks. In this process, aluminum and steel sheets of different thicknesses are welded together with high strength.

The basis of the new process is friction stir welding. In the welding process, a rotating tool (stirring) moves along the gap to be joined with a great deal of force (rubbing), thus joining the sheet metal blanks. According to Martin Werz from the Materials Testing Institute (MPA) at the University of Stuttgart, conventional arc welding of steel and aluminum produces brittle intermetallic joints. "Friction stir welding, on the other hand, produces high-strength and stable hybrid blanks," says Werz. These are also known as "Hybrid Tailor Welded Blanks". Werz explains the advantages of the process: "We can butt weld and overlap the sheets at the same time and thus achieve a larger cross-sectional area, which in turn ensures greater strength and consequently also greater formability." The seam is so stable that the hybrid blanks can even be deep-drawn. "Our weld seam holds even with complex geometries such as curves," says Werz.

Advantages for automotive production

The automotive industry in particular could benefit from the new process. Werz: "The advantages of thin sheets made of high-strength steels and aluminum sheets with a slightly higher thickness and the resulting higher buckling stiffness can be used in a component by combining both materials in a resource-saving way." Buckling stiffness is the resistance of a component to an elastic load perpendicular to the surface. This means that the material yields like a spring and returns to its original shape at the end of the load without having suffered a "dent".

The resulting seam is so stable that the hybrid blanks can even be deep-drawn. This allows lightweight and resilient components to be produced, for example for the automotive sector. © MPA Stuttgart

"Until now, hybridization in car body construction has only been achieved by assembling components made from different materials. Thanks to our developments, we are already making it possible to combine aluminum and steel in individual components. This opens up additional degrees of freedom in structural optimization, which can be used to reduce weight," says Werz. The expert also assumes that the weight of body shells can be reduced by around 10 percent by using hybrid blanks in car manufacturing - with the same level of safety. Less weight in turn leads to lower fuel consumption and reduced emissions.

In this video, the process of friction stir welding is explained briefly and clearly.

According to documents from Leichtbau BW / ag