Rapid Solidified Al Alloys and Al-based Composites

F. AUDEBERT; M. GALANO; G. W. SMITH

Congreso; ISMANAM 2009 - XVI International Symposium on Metastable and Nano Materials; 2009

Rapid solidification, severe plastic deformation or composite techniques have been used for many years for achieving Al-based materials with improved mechanical properties. Rapid solidification techniques, such as melt spinning or gas atomisation followed by consolidation processes lead to obtain Al alloys composed by small Al grain matrix, high solute content and high volume fraction of intermetallic particles. Moreover, those techniques also allowed obtaining hiperetuectic Al-Si alloys with high volume fraction of very refined Si particles. Among the Al alloys produced by rapid solidification the NanoQuasicrystalline alloys composed by submicron sized quasicrystalline particles embedded in an a-Al matrix have been produced with high strength at elevated temperature. Alternatively, severe plastic deformation techniques have been used to obtain Al alloys with very refined Al grains in order to increase strength. Al based composites have been developed and industrialized using carbon fibres and oxide dispersion in conventional Al alloys matrix. Powder metallurgy or squeeze casting techniques are used as the main routes for their processing. Beyond these conventional reinforcements, new phases and strategies appear as very promising for developing new Al based materials with enhanced properties. In order to understand the influence of the different types of new reinforcements (quasicrystals, transition metals particles and nanosized ceramic powder) and the processing routes (rapid solidification, compaction and extrusion) several Al based materials have been prepared. In addition, to compare the mechanical behaviour, pure Al and hypereutectic Al-Si extruded bars have been produced. The microstructure was characterised by means of X-ray diffraction, Scanning and Transmission Electron Microscopy and Differential Scanning Calorimetry. The mechanical properties were studied using Vickers microhardness, compression tests and tensile tests. The results are discussed considering the microstructure characteristics and different deformation and strengthening mechanisms that can be involved in each material.