Interfacial modification strategy to break through the strength and ductility trade-off in multi-walled carbon nanotubes reinforced titanium matrix composites

Multi-walled carbon nanotubes (MWCNTs) are one of the ideal reinforcements for metal matrix composites (MMCs), however, it faced a big challenge regarding their mechanical compatibility of MWCNTs reinforced titanium matrix composites (TMCs) due to its strong agglomeration, undesirable interfacial reaction and etc. To overcome this key problem, we employed Cu nanoparticles to decorate MWCNTs (Cu-MWCNTs) and successfully fabricated Cu-MWCNTs reinforced TMCs with the support of hot-pressed sintering (HPS) approach. The addition of Cu nanoparticles not only improved its dispersion, but also effectively reduced the interfacial reaction through the in-situ synthesized interfacial Ti2Cu phases and preserving the integrity of MWCNTs. Tensile studies reflected that the addition of 0.5 wt % Cu-MWCNTs was advantageous in improving the tensile properties, breaking through the trade-off between the strength and ductility, which were 15% and 45% higher than the matrix alloy, respectively. The quantitatively analysis of the increased strength proved that the primary strengthening mechanisms included the grain refinement, the solid solution of the carbon atoms from MWCNTs and the efficient load transfer from the multiple interfaces with in-situ synthesized interfacial Ti2Cu phases. The improvement in toughness was mainly derived from the high dislocation storage capacity induced by interfacial modification, thus achieving the higher uniform elongation in TMCs. Consequently, this work provided the promising approach to design strong and ductile TMCs.