Mechanism of titanium micro-alloying on interfacial bonding strength in Cu matrix composites: A combined experimental and DFT study

The interfacial bonding is a decisive factor for the performance of hybrid reinforced Cu matrix composites. This study presents a systematic investigation into the interfacial characteristics of Ti-doped graphene nanoplatelets (GNPs) and alumina whiskers (Al 2 O 3 ) co-reinforced Cu matrix composites via an integrated approach combining theoretical analysis with experimental methodologies, comprehensively evaluating the influence of Ti content on interfacial bonding behavior, microstructural evolution, and the resultant mechanical properties of the composites. The combined analysis through density functional theory (DFT) and thermodynamic calculations demonstrated that Ti preferentially segregates at Cu/GNPs and Cu/Al 2 O 3 interfaces to induce in-situ formation of nanoscale TiC interfacial phases, as validated by DFT calculations which show that Ti micro-alloying and TiC formation increase the Cu/GNPs and Cu/Al 2 O 3 interfacial binding energies by 5% and 17%, respectively. The TiC phases and residual Ti act as rivet-like interfacial structures to anchor the reinforcements with the Cu matrix, effectively suppressing dislocation motion and enhancing load transfer efficiency. Consequently, the synergistic strengthening effect of GNPs and Al 2 O 3 whiskers is significantly promoted, leading to a 133% increase in tensile strength and a 32.4% improvement in compressive strength of the composite with 4 wt.% Ti compared to the unalloyed counterpart. This study addresses the critical issue of interfacial incompatibility between dual reinforcements and Cu matrix, providing a cost-effective and scalable interfacial regulation strategy via Ti micro-alloying for high-performance hybrid reinforced Cu matrix composites.