Al Based Quasicrystalline Nanocomposites for Elevated Temperature Applications

  In recent years Al-Fe-Cr-Ti quascristalline alloys were developed, with a microstructure composed of quasicrystals of nanometre size embedded in an a-Al matrix. These alloys were generally produced by melt spinning, and showed high strength at elevated temperatures in comparison with commercial Al based alloys.  In early works by the authors, 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, Al-Fe-Cr-Nb alloys containing quasicrystals have become promising new high strength nanocomposites to be applied at elevated temperatures in the automotive and aerospace industries.

 To scale up and develop further these alloy systems for industrial applications, extruded bars have been produced from atomised powder. Different mixtures of atomised pure aluminium and nanoquasicrystalline powders containing Ti or Nb were used to produce nanocomposites. The microstructure of the atomised powders and extruded nanocomposite bars was characterised by means of XRD, SEM, TEM, EBSD, EDX and DSC. Mechanical properties have been studied by means of microhardness tensile and compression tests. The relationship between processing, microstructure and properties will be discussed. The extruded bars maintained good mechanical properties similar to those reported for as-melt-spun ribbons, thus offering an attractive processing route for larger-scale industrial applications.
 This work was supported by the UK Engineering and Physical Sciences Research Council and DSTL (EP/E040608/1.)