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SFB 692:  High-strength Aluminium-Based Light Weight Materials for Reliable Components

Subject Area Materials Science and Engineering
Mechanical and Industrial Engineering
Social and Behavioural Sciences
Term from 2006 to 2017
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 14208545
 
Final Report Year 2018

Final Report Abstract

The main objective of CRC 692 was to investigate and exploit the potential of aluminum-based lightweight materials, taking into account the different influences along the process chain during manufacturing of safety components. The research focused on the development, production and characterization as well as on the use of new lightweight materials in safety-related applications. One challenge was that material concepts and manufacturing processes had to be coordinated in such a way that high reliability requirements could be met throughout the entire product life cycle. Especially mass and cost reduction also played an important role in the CRC. Forming techniques represent a successful and highly efficient approach for producing excellent mechanical properties, such as high strength combined with good ductility. The research work in the CRC – which can be structured along the three main development lines "High-strength wrought Al alloys", "Aluminum Matrix Composites (AMCs)" and "High-strength Al-based composites" – therefore aimed at designing, manufacturing and refining aluminum-based lightweight materials in the light of high quality requirements. Research in the first development line was focused on the production of fine and ultrafine-grained (UFG) microstructures in high-strength Al alloys, which exhibit previously unattainable strength-ductility combinations and, in part, a significantly improved corrosion behavior. Grain refinement was achieved by Severe Plastic Deformation (SPD) processes, in particular by Equal Channel Angular Pressing (ECAP) and closely related processing techniques. In addition to the formation of UFG microstructures, these techniques were used to investigate the precipitation kinetics of age-hardening Al alloys. Optimized heat treatments could be developed, which allow an economic adjustment of the desired property combinations. In addition, extensive micro- and continuum-mechanical modeling allowed the elementary processes that occur in complex deformation paths to be studied in detail. Further investigations were carried out to investigate how UFG surfaces can be produced without cracking in graded semi-finished products (with conventional grain sizes in the core) and how microstructural gradients affect the properties of the semi-finished products. Additional research activities considered the novel approach to develop an SPD process for shaped parts, investigated how low temperatures affect the maximum achievable forming degrees, and analyzed within which process limits deformation localizations can be avoided in SPD processes. The second development line focused on particle-reinforced aluminum matrix composites (AMCs) as well as the machining or electrochemical micro-structuring of their surfaces. By high-energy ball milling, composite powders and compact semi-finished products were produced utilizing nano-scale hard particles and the gas pressure infiltration process. The AMCs have a high potential, e.g., for applications where elevated temperatures and / or tribological loads occur. Therefore, especially in the third funding period, in addition to new consolidation procedures and the creation of tailor-made matrices by varying the alloying elements, the thermal stability of the AMCs at elevated temperatures was carefully investigated. The third development line was initially limited to the investigation of aluminum-coated magnesium composites, which combine additional mass reduction with good corrosion protection. For a successful implementation of this concept, microstructural and micromechanical processes at internal interfaces and outer surfaces were examined in detail. In the third funding period, additional focus was placed on composites with steel materials, which significantly expanded the potential range of applications for high-strength aluminum-based materials. The joint research and collaboration of the scientific subprojects in five working groups allowed to systematically consider topics of general importance such as low temperature forming, thermal stability and joining with other material classes, which are of particular relevance for the application of high strength Al-based materials in industrial practice. In the second and third funding period, a total of seven transfer projects were successfully initiated, where, together with industry partners, the fundamental knowledge of the engineering science-focused CRC was transformed towards industrial application.

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