Enhanced mechanical properties of alloyed copper matrix composites reinforced with partially-unzipped carbon nanotubes

Sufficient interfacial contact and adhesion are important factors for ensuring effective load transfer in carbon nanotubes (CNTs)-reinforced copper matrix composites (CMCs). In this study, a chemical unzipping method and matrix-alloying (addition of Cr) were integrated to solve these two challenges in CMCs. The results showed that partially-unzipped CNTs (PUCNTs) improved the restricted interfacial contact areas of CNTs. Furthermore, the graphene layers of PUCNTs might improve the interfacial shear strength, and fully utilize the load transfer capacity of the inner walls. Trace amounts of interfacial carbides (Cr7C3 or Cr23C6) were formed in situ at the PUCNTs/CuCr interface, which further improved the interfacial bonding between PUCNTs and the CuCr matrix. The ultimate tensile strength (382.9 MPa) and elongation (37.02%) of the 2 vol% PUCNTs/CuCr composite were higher than similar reported materials. A balance between the strength and ductility of the PUCNTs/CuCr composites was obtained. This was ascribed to the combined effects of the interfacial carbides and interfacial contact area, which improved the load transfer ability and interfacial adhesion, and also promoted dislocation accumulation ability of the PUCNTs. The strengthening effect of PUCNTs was also investigated using the correctional shear-lag strengthening and dislocation strengthening models. This work shows that PUCNTs are better reinforcement fillers than CNTs for enhancing the mechanical properties of CMCs.