Microstructure and mechanical properties of Ti6Al4V-(TiC+TiB)/Ti laminated composites fabricated by hot press plus hot rolling

The prevalent issue of poor ductility in titanium matrix composites severely restricts the development and application of these materials. In this work, the laminated titanium matrix composites consisting of ductile Ti6Al-4V layer and (TiC+TiB)/Ti composite layer were successfully designed and fabricated by vacuum hot pressing plus hot rolling. A systematic investigation of the microstructural evolution, mechanical properties, strengthening and fracture mechanisms of the laminated composites has been conducted. The results indicate that the composite possesses a laminated structure, with the interfaces being free from delamination, porosity, and other defects, achieving a firm interfacial bonding. And the tensile testing results indicate that the composite shows superior strength-toughness synergistic properties due to the configuration design of laminated structure, with tensile strength and fracture strain reaching 1103.69 MPa and 13.04 %, respectively, which represent an enhancement of 11.67 % and 86.02 % over the (TiC+TiB)/Ti composite. The increase of strength was mainly attributed to grain refinement strengthening, second-phase strengthening and heterogeneous structure strengthening. Fractographic analysis reveals that crack deflection and the elongation of the crack propagation path are the primary causes for the increase in fracture strain. This work provides a new approach to the forming and manufacturing of high-quality laminated titanium matrix composites with synergy of strength and ductility.