Carbon nano-rods reinforced powder metallurgy aluminum composites

Multi-wall carbon nanotubes (CNTs) were uniformly mixed with pure aluminum (Al) powder by high-energy planetary ball milling process, and Al powder surface coated with CNTs was prepared. These Al based composite powder were completely consolidated via solid-state sintering and hot extrusion process. By changing the sintering temperature, CNTs could be easily transferred to nano-scale carbides, which are also effective reinforcements of the composites. CTNs fully reacted with Al matrix, and resulted in formation of Al₄C₃ nano-rods dispersed in the Al matrix. The nano-dispersoids and grain refinement of α-Al caused the significant improvement of mechanical strength of pure Al matrix composites. With increase in the CNTs content, yield stress and tensile strength of Al-Al₄C₃ composites were significantly improved; for example, in case of 2wt% CNT addition, the composite material showed a good balance between 396 MPa UTS and 11.7% elongation at the ambient temperature. The mechanical properties at the elevated temperature were also improved by using Al₄C₃ reinforcements.