New metal matrix composites with fullerene dispersion fabricated by friction stir processing

Fullerene was successfully dispersed into various metals such as AZ31-O, A5083-O, and C1020-O using Friction Stir Processing (FSP). The dispersion of the fullerene promoted the grain refinement of the metal matrix by FSP. Especially, the grain size of the AZ31 amazingly decreased by the uniform distribution of the fullerene molecules. The stir zone of the FSPed AZ31 with the fullerene consisted of ultra-fine grains which should be less than 100 nm. The grain size of A5083 and C1020 was also refined to ∼200 nm. The maximum microhardness of the fullerene/AZ31 nanocomposite reached ∼126 HV, which is almost three times higher than that of the AZ31 substrate. Additionally, the fine grain and high hardness of fullerene/AZ31 nanocomposite are maintained at the elevated temperature. It is considered that fullerene is the ultimate material for the metal matrix as the additive to refine the grains and enhance the mechanical properties due to its extremely small size and excellent physical properties. Our results show that the FSP with the fullerene is very attractive for the metal matrix to decrease the grain size and increase the mechanical properties.