Synergistic strength-ductility improvement of (TiB+TiC/Ti6Al4V)–Ti6Al4V composites through laminated structural designs

In order to resolve the conflict between strength and ductility in titanium matrix composites (TMCs), we designed a novel laminated Ti6Al4V (Ti64)-TMCs composite using laser melting deposition. Six configurations with varying layer thicknesses were engineered to achieve continuous microstructural gradients. Key findings reveal that the TMCs layer (8-18 μm grains) promotes heterogeneous nucleation through in situ reinforcement, while the transition layer (19-30 μm grains) bridges structural hierarchies. The Ti64 matrix maintains prior β-columnar grains, collectively forming an equiaxed-columnar gradient structure. Layer thickness critically influences elemental diffusion and defect dynamics: Thicker Ti64 layers impede B/C element migration, inducing grain boundary dislocation pile-ups in TMCs layers, while increased TMCs layer thickness reduces geometric dislocation density. This hierarchical design overcomes traditional trade-offs by strategically managing stress distribution and crack propagation pathways. Our work establishes a multiscale structural paradigm that resolves the longstanding strength-ductility conflict in titanium composites, providing fundamental insights for engineering high-performance structural materials through controlled microstructural gradation.