Strengthening mechanisms in whisker-reinforced aluminium composites

Abstract

Silicon carbide whisker reinforced aluminium alloys were mechanically tested in the as-cast and heat treated conditions; the microstructures were examined by transmission electron microscopy. The mechanical properties were strongly dependent upon the nature of the matrix alloying elements, the heat treatment conditions and the processing routes. Al-Cu and Al 6061 reinforced alloys were very responsive to heat treatment while Al-Mg and Al-Si reinforced alloys were not. The microstructures and mechanical properties were analysed in an attempt to determine the operative strengthening mechanisms and deformation processes. Three distinct types of matrix microstructure were observed, distinguished by the presence or absence of subgrains and/or precipitates. Using these observations, the composite properties could be quite well modelled using dislocation theories, indicating that the matrix microstructure dominates the mechanical properties.