Abstract: Reinforcing metal matrix composites (MMCs) with nanophases of distinct characteristics is an effective strategy for utilizing their individual advantages and achieving superior properties of the composite. In this study, a combination of molecular level mixing (MLM), segment ball milling (SBM), and in-situ solid-phase reaction was employed to fabricate Cu matrix composites (TiC-CNT/Cu) reinforced with TiC decorated CNT (TiC@CNT) and in-situ nanoscale TiC particles. The HRTEM results revealed the epitaxial growth of interfacial TiC on the surface of CNT (i.e., CNT(0002)//TiC(200), and the formation of a semi-coherent interface between TiC and Cu matrix, which can effectively enhance the interfacial bonding strength and optimize load transfer efficiency of CNT. The independent in-situ TiC nanoparticles got into the grain interior through grain boundary migration, thereby significantly enhancing both strain hardening capacity and strength of the composite by fully utilizing the Orowan strengthening mechanism. Moreover, the enhanced bonding strength of the interface can also effectively suppress crack initiation and propagation, thereby improving the fracture toughness of the composite. The TiC-CNT/Cu composite with 1.2 vol.% CNT exhibited a tensile strength of 372 MPa, achieving a super high strengthening efficiency of 270, while simultaneously maintaining a remarkable ductility of 21.2 %. Furthermore, the impact toughness of the TiC-CNT/Cu composite exhibited a significant enhancement of 70.7 % compared to that of the CNT/Cu composite, reaching an impressive value of 251 kJ/m², thereby demonstrating exceptional fracture toughness. Fully exploiting the synergistic strengthening effect of different nanophases can be an effective way to improve the comprehensive properties of MMCs.

Key words: CNT/Cu composite, Double nanophases, Intragranular in-situ TiC, Strength-ductility balance, Interface optimization