Strengthening and toughening of aluminum by single-walled carbon nanotubes

▶ SWNTs are effective to enhance strength, ductility, and toughness of composites. ▶ The deformation mode of the matrix affects the load transfer efficiency. ▶ Strengthening efficiency of SWNTs is halved in the nanocrystalline aluminum. Effects of single-walled carbon nanotubes (SWNTs) on strengthening and toughening behaviors of aluminum-based composites with grain sizes ranging from nano- to micrometer have been investigated. The strength of composites is enhanced as an increase in SWNT volume and a decrease in grain size. Nanocrystalline composite containing 3.5vol.% SWNTs exhibits good ductility of ∼5% tensile elongation to failure as well as superior yield stress of ∼600MPa. However, the strengthening efficiency of SWNTs becomes half of the theoretical prediction for nanocrystalline composites due to the recovery process around the interface. Nanocrystalline composite containing 2.0vol.% SWNTs shows the fracture toughness of ∼57MPamm1/2, which is five times higher than that of starting aluminum. SWNTs may effectively block the propagation of necks and cracks, providing much improved ductility and toughness.