Simultaneous enhancement of strength and ductility in additively manufactured pure titanium via in situ TiB reinforcement

Achieving a favorable strength-ductility synergy in commercially pure titanium remains a long-standing challenge, especially in ceramic-reinforced titanium matrix composites where strength enhancement is typically accompanied by ductility degradation. In this work, in situ TiB-reinforced pure titanium composites were fabricated via directed energy deposition (DED) using TA1 powder and TiB 2 as precursors, and the influence of TiB 2 content on microstructure evolution and mechanical behavior was systematically investigated. The results revealed that 1 wt.% TiB 2 addition enabled a simultaneous improvement in strength and ductility. Compared with monolithic TA1, the yield strength increased from 462.5 MPa to 541.1 MPa, and the fracture elongation improved from 19.61% to 21.40%. Kernel average misorientation analysis indicates that intragranular TiB precipitates enhance dislocation storage and strain hardening capability, thereby promoting homogeneous plastic deformation and delaying plastic instability. 3 wt.% TiB 2 addition leads to preferential grain-boundary TiB segregation and severe strain localization. First-principles simulations further demonstrate strong TiB/α-Ti interfacial bonding, ensuring efficient load transfer during deformation. The strengthening and toughening mechanism was discussed in detail. These findings identify a critical TiB 2 content window for achieving strength-ductility synergy in additively manufactured pure titanium.