Nano-silicon carbide reinforced aluminium produced by high-energy milling and hot consolidation

► Aluminium reinforced with ex situ nano-SiC by powder metallurgy technology. ► Nature of the SiC nanoparticles and high-energy mixing methods are investigated. ► Effective nanoparticle dispersion estimated, using matrix crystallite size. ► 10 vol.% of SiC nanoparticles effectively mixed in aluminium for tensile response. High-energy milling was studied for the ex situ strengthening of aluminium with silicon carbide (SiC) nanopowders. Heptane was used as a milling agent for both planetary- and attritor ball milling. Considering the different milling techniques and the differences in the resulting powders, effective dispersion of the nano SiC was achieved. Composite samples compacted by hot pressing showed an increase in hardness (HV 20 = 220) and a decrease in Al crystallite size from 220 to 55 nm with the nano-SiC content increasing from 1 up to 20 vol.%. The ultimate tensile strength was measured for extruded samples which resulted in 205 MPa (17% elongation) for 1 vol.% of nano-SiC and a strength of 420 MPa (4% elongation) for 10 vol.% of nano-SiC reinforcement. The mechanical properties were compared with what was predicted by the Hall–Petch relationship.