Nanostructured Al-based Matrix Composites

M. GALANO; F. AUDEBERT; A. MARSH; M. RAMUNDO

Cancun

Simposio; XXI International Symposium on Metastable and NanoMaterials (ISMANAM 2014); 2014

Aluminium quasicrystalline alloys have been studied in the past years achieving high strength and retaining the low density characteristic of Al alloys. In this work aluminium quasicrystalline alloy nanocomposites have been manufactured for the first time using ball milling and extrusion. For that purpose nanoquasicrytsalline Al-Fe-Cr based alloys had to be manufactured by powder atomisation thus the powder atomisation production was investigated. The powders microstructures were characterised and mechanical properties of hot extruded bars were measured at room temperature and elevated temperatures. It was observed that a very high temperature is required to produce these alloys by gas atomization; the icosahedral quasicrystalline phase can be retained after the atomization in powder sizes typically under 75µm, and also after the extrusion at 375°C. Nanocomposites consisting of a quasicrystalline Al-Fe-Cr based alloy matrix and reinforcement of nanoceramic particles were manufactured with different volume fractions. The effect of ball milling time on the microstructure and microhardness of the nanocomposite powders was investigated. Bulk materials were produced by consolidation and hot extrusion. The phase characteristics and microhardness of the extruded materials were investigated. The milling regime behaviour was identified, and shown to have a significant effect on the rate of change of uniformity of the reinforcement distribution. No significant decomposition of the quasicrystalline phase occurred over 30 hours of milling. Strain increased and the crystallite size of the aluminium phase decreased with milling time, with the aluminium crystallite size reaching a steady state. Although the quasicrystalline phase decomposed during extrusion, the microhardness of the nanocomposites produced were significantly harder than both the unreinforced quasicrystalline alloy and crystalline aluminium nanocomposites encountered in the literature. The methods and analysis of material behaviour put forward in this work will inform further understanding and optimisation of this and other nanocomposite systems.