Synthesis of Non-Equlibrium Alloys by Friction Stir Processes

• Applicants: Professor Dr. Ferdinand Haider; Professor Dr.-Ing. Michael Friedrich Zäh
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Synthesis and Properties of Functional Materials ; Production Automation and Assembly Technology
• Term: from 2016 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310621524

Friction Stir Welding (FSW) is a solid-state joining technique in which the adhesive bonding is produced by a local plastification and mechanical stirring the abutting surfaces of the joining partners.The achieved joint properties can reach very high qualities due to the finegrained microstructure, which is caused by the dynamic recrystallization of the material in the process zone. This advantageous modification of the microstructure is targeted at Friction Stir Pro-cessing (FSP). Instead of joining a pure material treatment is the aim of this process variant. The FSP is used to refine the microstructure of workpieces locally. Both Friction Stir techniques (FSW and FSP) have in common, that usually no filler metal is used. However, the possibility of thermomechanical alloying by Friction Stir techniques is absolutely given. Several scientific publications indicate, that for example through the FSP technique solid connections and occasionally even a verifiable alloying between the inserted additives and the base material are producible. Furthermore, as part of the preparatory work, it was shown, that a specific alloying of FSW seam with a welding filler metal is basically possible by the formation of intermetallic phases in the solid state. However, the described results are mainly based on material science investigations and have rarely been attributed to procedural operations. Thus, a comprehensive knowledge of the alloy forming processes, their influencing variables and a way to control this process through technical procedures still lacks. The aim of the project is to gain understanding of the possible application of Friction Stir techniques as a method for the production of non-equilibrium alloys or of materials with locally modified composition. For this, a deepened understanding of the process related requirements on the one hand and on the other hand of the metallurgical operations during the mechanical alloying of metals by Friction Stir techniques will be investigated. The research of production engineering will focus on a homogeneous distribution of the applied filler material and determining or generating a suitable process temperature. Referring to material science the focus will be on the analysis of alloying and the properties of the produced alloys. The new acquired knowledge will finally lead to a coupled process and material model for describing the mechanism of alloy formation and controlling.

• DFG Programme: Research Grants