Fabrication of carbon nanotubes/Cu composites with orthotropic mechanical and tribological properties

Highlights: • Ni–Cu coating on MWCNTs improves the interface bonding of MWCNTs/Cu. • MWCNTs are uniformly dispersed in the Cu matrix by ultrasonic and nitrogen-assisted stirring. • The mechanical and tribological properties of composites show orthogonal anisotropy due to the oriented MWCNTs. In this work, Multi-Walled Carbon Nanotubes reinforced copper matrix composites were prepared through a series of preparation processes including ultrasonic and nitrogen-assisted mixing, electroless Nickel–Copper bilayers plating, hot extrusion and cold drawing. The mechanical and tribological properties of the composites were enhanced with the increase of MWCNTs. The Cu matrix composites enhanced with 10 vol% MWCNTs showed significant improvements in the mechanical and tribological properties. Compared with the pure Cu sample prepared by the same method, the tensile strength and yield strength of the composite increased by 52.15% and 56.67%, while the friction coefficient and wear rate decreased by 66.8% and 62.3%, respectively. Better than most of the reported data. The 3 vol% MWCNTs in the composites exhibited the highest strengthening efficiency. Due to the directional arrangement of the MWCNTs in the Cu matrix, the composites showed obvious orthogonal anisotropy, and the properties in the parallel drawing direction were much better than those in the vertical drawing direction. Dislocation and load transfer effect are considered as the main mechanism of mechanical properties enhancement. The formation of self-lubricating layer, load transfer, efficient derivation of friction heat and orientation arrangement of MWCNTs were the reasons which lead to the friction performance enhancement.