Microstructure and mechanical properties of 6061 Al alloy based composites with SiC nanoparticles

Materials with high specific strengths as well as damage tolerance are of great importance for automotive and aerospace applications. Ceramic reinforced metal matrix composites (MMCs) show good potential for these uses but have been hampered by insufficient ductility and production issues, both of which this work looks to resolve. Nanoparticle reinforced 6061 aluminium alloy matrix composites have been produced by a powder metallurgy route and shown to exhibit high strength and Young's modulus alongside good ductility and low density. A powder metallurgy route consisting of high energy ball milling, hot isostatic pressing (HIP) and extrusion has proved a highly effective process for achieving a homogeneous distribution of particles, with minimal clustering of the nanoparticles, at an industrially relevant scale. After heat treatment the composites display high strengths, owing to SiC nanoparticle reinforcement as well as the age hardening effect. The remarkable feature of nanoparticle reinforced MMCs compared to micron size reinforcements is that particle fracture does not occur and effective particle-matrix bonding can be taking place, resulting in a greater combination of strength and toughness. The combination of properties achieved by the composites studied in this work are superior to most of the micron sized particle reinforced MMCs reported elsewhere and are well beyond what is possible with traditional aluminium alloys.