Investigation of precipitation-hardenable-, copper-base-alloys, for brazing of materials with highly different coefficients of thermal expansion.

• Applicant: Professor Dr.-Ing. Wolfgang Tillmann
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 281583335

In various applications, the rising requirements concerning the mechanical and thermal properties as well as corrosion resistance cannot be met by conventional metallic materials. Due to this fact, the use of combinations of high-performance partially or fully ceramic materials and ductile metal supporters becomes increasingly important. In order to create high-strength joints with specific properties it is often necessary to join these parts with a fusion based process. Here, brazing is broadly applied. A difficulty, which hinders the use of the full potential of the created joints, is the distinctive development of residual stresses during brazing. This is the result of the often significantly different coefficients of thermal expansion of the used materials. To obtain a reduction of the stresses, ductile filler metals are used. However, these alloys possess only limited strength against external forces. Consequently, an ideal filler metal should be both ductile enough to relax residual stresses and tough enough to create high-strength joints. These requirements can be met by hardenable alloys, as long as there are suitable alloys available and the metallurgic mechanisms are known and understood. The main task of the proposed work is the analysis of hardenable alloys in the context of brazing. Contrary to the casting of such alloys, the microstructural evolution undergoes much more complex processes. Especially the diffusion-kinetics phenomena in multi-component system have to be considered intensively. To do so, selected alloys will be analyzed on their own, in interaction with one substrate as well as in the whole joint. The effects of the substrates on the hardening behavior can be identified and determined using this attempt. The gained knowledge will be applied in the final stages of the project to join application-related components in order to reveal the potential of the new alloys and compare it to conventional filler metals. The combination of the results of both investigations provides a profound scientific fundament for possible application-oriented development of filler metals for the described special applications.

• DFG Programme: Research Grants