Using direct high-pressure torsion synthesis to produce aluminium matrix nanocomposites reinforced with carbon nanotubes

Aluminium matrix nanocomposites reinforced with carbon nanotubes were fabricated in a new way by direct synthesis using high-pressure torsion (HPT). Aluminium of 99.99 % and 99.5 % purities were used as matrix materials with carbon nanotubes in amounts of 0.5 and 1 wt% as reinforcement. The HPT processing led to extensive grain size refinement which was significantly higher than for pure metals and to a relatively uniform distribution of the fillers. The grain size of the matrix was smaller for Al99.5 compared to Al99.99 while the particle spatial distribution was more homogenous for the Al99.99 matrix. This was attributed to a lower hardness and higher plasticity of Al 99.99 alloy. The addition of carbon nanotubes also improved the thermal stability of the ultrafine-grained structure, especially if homogenously distributed as for the Al99.99 matrix nanocomposites.