Microstructure and mechanical properties of carbon nanotubes reinforced titanium matrix composites fabricated via spark plasma sintering

The influence of various dispersion methods on the evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via spark plasma sintering (SPS) have been investigated. The synthesis procedures included sonication, high energy ball milling (HEBM), and rapid consolidation of powder mixtures at different sintering temperatures. The impact energy provided to the powder mixtures during HEBM process was optimized to disperse 0.5 wt% MWCNTs into Ti matrix in two controlled ball milling processes: with and without in-situ formation of TiC during HEBM. The interfacial reactions between MWCNTs and Ti matrix were controlled by retaining the crystallinity and sp2 carbon network of the MWCNTs even at high sintering temperature of 800 °C, which enhanced their compressive strength up to 1056 MPa with a compressive strain of 27.31%. The mechanical and tribological properties of the composites consolidated from the powder mixtures with in-situ TiC formation during HEBM and pre-sonicated MWCNTs were significantly enhanced as opposed to the composites consolidated from the powder mixtures without formation of TiC during HEBM.