Search

CNTs/Cu composite powders were prepared by an electroless plating and planetary ball milling process. The structure of composite powders was investigated. Results showed that Cu particles are homogeneously deposited on CNTs surface, and CNTs are deeply embedded into Cu matrix after milling, which play an important role in the dispersion and the wettability of CNTs within matrix and subsequently in the mechanical properties of composites. And the bulk CNTs/Cu was fabricated by vacuum sintering, re-pressing and re-sintering, and cold drawing process. It revealed that comparing pure Cu and composite without electroless plating, the tensile strength of composite with electroless plating increases obviously, up to 207 MPa. SEM images revealed that agglomeration is the main reason of deteriorating mechanical properties of composites. Finally, higher strength composites were successfully obtained by cold drawing. Results demonstrated that it can significantly improve the mechanical properties of the composites. Also, the tensile strength and the yield strength are up to 311 MPa and 185 MPa, respectively. SEM images clearly revealed that it is the dispersion and directional distribution of CNTs in matrix that further improve the strength of composites in drawing orientation. The load transfer theory was also employed to testify the results, effectively.

Titanium alloys have been applied for many lightweight structural components in the fields of aerospace, automobiles and biomedical implants owing to their light-weight, good mechanical properties and biocompatibility. However, poor tribological performance often restricts their wide-range applications. In this study, we synthesized Cu modified Ti-6Al-4 V (TC4) powders with various Cu contents (0, 1, 3, 5, 10 wt%), which was further strengthened with 0.3 wt% graphene oxide nanosheets (GONs) using a powder metallurgy technology. These composite powders were then synthesized into titanium matrix composites using spark plasma sintering. Effects of Cu contents on microstructure evolution, phase composition and tribological properties of Ti matrix composites were systematically investigated. The synthesized composites were consisted of α-Ti, β-Ti, Ti2Cu, in-situ-formed TiC and remained GONs, and showed better tribological properties than those of TC4 alloy. The average coefficient of friction was reduced from 0.168 to a minimum value of 0.120 as the copper content increased from 0 to 3 wt%, meanwhile the wear volume loss was reduced by 49.3%. Whereas further increasing Cu contents resulted in the increases of both coefficients of friction and wear volume loss. These improvements are mainly attributed to the hardness strengthening effects by Ti-Cu intermetallics and TiC@GONs structure, as well as the self-lubricating effect of GONs. Compared with traditional surface modification processes, the new method proposed in this work is cost-effective and promising for improving the tribological performance of titanium alloys in industry applications.