Synthesis, characterisation and mechanical properties of SiC reinforced Al based nanocomposites processed by MA and SPS

Al based alloys reinforced with different amounts (5, 12 and 20 wt-%) of nanosized SiC particulates were synthesised by mechanical alloying and consolidated by the spark plasma sintering (SPS) technique. The distribution of the reinforcement phase in the composite was evaluated as a function of the milling time and the amount of SiC. The processed materials were characterised by scanning electron microscopy and energy dispersive spectroscopy for the morphology and composition and X-ray diffraction. Continuous reduction in crystallite size was observed as milling progressed and after milling for 20 h the resulting powders reached a grain size of <100 nm. These Al-SiC composites were successfully consolidated by the SPS method at different sintering temperatures of 400, 450 and 500 degrees C. It is suggested that a higher hardness can be achieved even at 20 wt-% SiC when a higher sintering temperature, for example, above 500 degrees C, is used.