Challenges for Research and Development of New Aluminum Alloys

Aluminum alloys show a low weight, relatively high specific strength, good corrosion resistance in neutral environments and high electric and thermal conductivity. It makes them of interest for production of various functional components in aerospace and automotive industry. Wrought alloys generally have good formability and they are processed by common technologies, such as extrusion, forging, rolling, drawing etc. Complex shape components are also produced from casting alloys, mainly Al-Si-based, by various casting processes, like gravity casting, centrifugal casting, die casting etc. Industrial development of Al-based alloys is conservative, because it is mostly concentrated on modifications of common and well known alloy systems (Al-Cu, Al-Si, Al-Mg-Si, Al-Zn-Mg, Al-Li-Cu etc.) and processing routes. The reason is that there is a lack of experience in new alloy systems and production methods. However, standard systems stated above seem to approach their mechanical limits. By appropriate thermo-mechanical processing routes, i.e. combination of forming and age hardening, so-called high-strength alloys (Al-Zn-Mg or Al-Li) can reach a maximum tensile strength of about 700 MPa. To exceed this limit, qualitatively new alloys and processing routes should be developed. In addition, common high-strength alloys generally show low thermal stability, i.e. fast reduction of strength at temperatures above 200 °C. The poor thermal stability is a consequence of relatively high diffusion coefficients of the main strengthening elements (Cu, Mg, Zn) in solid aluminum. Therefore, for elevated temperature applications, new additives to Al should be used.