Manufacture and Characterization of Bulk Nanoquasicrystalline Aluminium Alloys and Composites for High Strength Applications

M GALANO; N ROUNTHWAITE; S PEDRAZZINI; W GU; F AUDEBERT; G D SMITH

Cranfield

Workshop; HIPERNANO 2010: Nano-enhanced Materials for Challenges in Auto & Aero; 2010

Al based quasicrystalline alloys which have a microstructure composed of nano-quasicrystalline particles embedded in an a-Al matrix exhibit high strength in comparison with commercial Aluminium alloys. In particular, Al-Fe-Cr-Ti nanocomposites produced by melt spinning [1] showed high strength at elevated temperatures. In early works by the authors [2], it was observed that the substitution of Ti by Nb increased the stability of the quasicrystalline phase delaying the microstructural transformation to higher temperatures. Thus, these nanocomposites containing Al-Fe-Cr-Nb quasicrystals have become promising new high strength nanocomposites to be applied at elevated temperatures in the automotive and aeronautical industries. However, these alloys were unable to be taken further into industry due to the unavailability of scaling up the manufacturing processes without hindering their mechanical behaviour. The present work summarises the achievements on the development of bulk nanoquasicrystalline alloys and composites within an EPSRC/MoD funded project carried out at the Department of Materials, University of Oxford. Pure nanoquasicrystalline alloys with increased stability were developed in bulk shape and subsequently bulk nanocomposites were also obtained by the addition of different volume fraction pure Aluminium particles. The bulk material was obtained by powder atomisation followed by extrusion. The microstructure of the atomised powders and extruded bars was characterised by means of XRD, SEM, TEM, EDX and DSC. Mechanical properties have been studied by means of microhardness, compression and tensile tests at room and elevated temperatures. The relationship between processing, microstructure and properties has been analysed. Different aspects of the manufacturing processes and microstructural characteristics as oxide particles and grain sizes are been analysed carefully achieving the balance needed to allow the scalability to near industrial scale without compromising the mechanical behaviour. The extruded bars maintained good mechanical properties similar to the reported for the as melt spun ribbons [3], thus, offering a feasible alternative for industrial applications.