Carbon nanotube reinforced aluminum composite fabricated by semi-solid powder processing

Semi-solid powder processing (SPP) is a promising technology that combines the benefits of semi-solid forming and powder metallurgy. In this study, carbon nanotube (CNT) reinforced aluminum alloy 6061 (Al6061) composite was synthesized by SPP for the first time. Mechanical alloying was used to disperse the CNTs in the matrix phase. The effects of the processing temperature (600 °C, 620 °C and 640 °C) on the microstructure, hardness, fracture surface and composition of the Al6061-CNT composite were investigated. Overall, the Al6061-CNT composite showed full densification above 99% with 100 MPa of pre-compaction and 50 MPa of pressure during consolidation in the semi-solid regime. Microstructure and the fracture surface analyses showed that the CNTs were uniformly dispersed throughout the Al6061 matrix. Higher density composite was obtained at higher liquid content, although the highest composite hardness was achieved when processed at 620 °C. It was speculated that the formation of carbides at higher temperatures affected the interface bonding between the matrix and CNT. The study showed feasibility of manufacturing CNT reinforced metal composites by SPP.