Mechanical properties and strain hardening behavior of aluminum matrix composites reinforced with few-walled carbon nanotubes

Abstract

In this study, for the first time few-walled carbon nanotubes (FWCNTs) with ∼3 walls were used as reinforcements in fabricating high performance aluminum matrix composites (AMCs). FWCNTs/Al composites and referential Al materials were prepared by a powder metallurgy route consisting of high energy ball milling, spark plasma sintering (SPS) and subsequent hot extrusion. It is found that, by decreasing SPS temperature and time, FWCNTs/Al composites showed reduced grains with an increased dislocation density and improved structural integrity of FWCNTs, leading to an increased tensile strength. Meanwhile, comparatively high strain hardening rates and long strain softening behavior were observed after necking in the sample sintered at 500 °C, which resulted in a tensile elongation of 11.7% with a high yield strength of 382 MPa. The experimental results suggested that, compared with traditional multi-walled carbon nano-tubes (MWCNTs), FWCNTs showed a noticeably enhanced strengthening effect and provided a good balance of strength and ductility in Al composites. It may make FWCNTs a good reinforcement candidate for metal matrix composites to achieve improved mechanical properties.