Structural characterisation and mechanical properties of nanocomposite Al-based alloys

Abstract

Nanocomposite Al-based alloys can be obtained with a combination of amorphous, crystalline and quasicrystalline phases. In order to understand the correlation between the nanostructure and the mechanical behaviour, four nanocomposite alloys with different characteristics were studied: two alloys from the Al-Fe-Cr-Ti system consisting of a spherical nanoquasicrystalline phase in an α-Al matrix; one alloy from the Al-Fe-V-Ti system consisting of a mixture of amorphous and α-Al phases; and one alloy from the Al-Mn-Cr-Cu system consisting of nanocrystalline particles embedded in an α-Al matrix. Melt-spun samples were prepared and the structure was characterised by means of X-ray diffraction and transmission electron microscopy. Differential scanning calorimetry was used to study the thermal stability and the transformation processes. Tensile tests, fractographic analysis and Vickers microhardness at room temperature were performed in order to evaluate the mechanical behaviour. A combination of solid solution, particle dispersion and grain refinement strengthening was responsible for the high strength of the alloys. The microstructure of the alloy Al93Fe3Cr2Ti2 (at%) remained acceptably stable up to 703 K, due to the slow coarsening rate of the icosahedral phase.