Manufacturing of application-specific components from particlereinforced aluminium matrix composites using a combination of powder presses and thixoforging

• Applicant: Professor Dr.-Ing. Mathias Liewald
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447676980

Aluminium matrix materials can be improved or modified in terms of hardness, elastic modulus, and strength by introducing particulate hard phases (e.g. silicon, oxides, carbides). Additionally, such aluminium matrix composites (AMC) can exhibit increased thermal stability and/or wear resistance compared to monolithic materials. Potential applications for such particle-reinforced AMC include components with specific application requirements, such as ventilated brake discs and brake callipers. However, production of such components, especially those with particularly high particle contents of over 30vol.%, currently is restricted by conventional powdermetallurgic or casting processes due to the challenging forming and flow behaviour of these AMC. Therefore, the scientific objective of this research project is to develop a process route for the manufacturing of application-specific components with particularly high particle contents and to determine the achievable material properties. The approach pursued combines powder pressing with thixo-forging. This combined process aims to produce complex components with varying wall thicknesses from AMC preforms with different particle contents (up to 50vol.% SiC particles), thus allowing for the near-net-shape manufacturing of components with precisely tailored, application-specific properties. In the first funding period, the feasibility of this process route for manufacturing components with 50vol.% SiC was successfully demonstrated, resulting in a significant increase in hardness and a reduction in thermal expansion. However, this was offset by a decrease in ductility and tensile strength of the components produced. The numerical and experimental research work of the second funding period therefore aims to deepen the understanding of the process with regard to a varying size ratio between the Al and SiC particles used, as these material parameters had a significant influence on the achievable process and component quality. Furthermore, the production steps of the developed process route will be extended in such a way that components with a graded distribution of the reinforcing particles can be produced. In this way, the advantages (high hardness, low thermal expansion) and disadvantages (low ductility and tensile strength) resulting from the particle reinforcement can be specifically adapted to component-specific requirements. Finally, the tribological behaviour of the graded AMC components will be characterized in order to demonstrate their application potential.

• DFG Programme: Research Grants