Reinforcement with in-situ synthesized carbon nano-onions in aluminum composites fabricated by flake powder metallurgy

Bulk aluminum matrix composites reinforced with carbon nano-onions (CNOs) were fabricated by a flake powder metallurgy route. Homogenous dispersion of CNOs (with an average size of ∼20 nm) was guaranteed by in situ polymer pyrolysis chemical vapor deposition of the precursor on Al nanoflakes with high specific surface area, followed by consolidating the CNO/Al nanoflake powders and then hot extrusion. The uniformly dispersed CNOs in ultrafine grained Al matrix exhibited remarkable strengthening efficiency: the 1.2 wt.% CNO/Al composite had a yield strength of 268 MPa and an ultimate tensile strength of 384 MPa, improved by 77% and 56% as compared to the Al matrix without CNOs, respectively. The strength enhancement with the in-situ CNOs is mainly attributed to a combined mechanism of grain boundary strengthening and Orowan strengthening.