Overcoming the strength-ductility trade-off dilemma in TiBw/TC18 composites via network architecture with trace reinforcement

In order to improve the ductility of TC18 (Ti–5Al–5Mo–5V–1Cr–1Fe) titanium alloy without sacrificing its strength, TiBw/TC18 composites with low reinforcement content (≤2.0 vol%) were designed and successfully fabricated. The large spherical TC18 powers and fine TiB₂ particles were selected for low energy ball milling (LEM) followed by reaction hot pressing (RHP) process. In situ synthesized TiB whiskers by Ti and TiB₂ reaction are distributed only on the surface of spherical TC18 powders, generating a three-dimensional network microstructure. The results showed that both the tensile strength and elongation of the as-sintered 0.5 vol% TiBw/TC18 composite (1171 MPa, 15.6%) were remarkably enhanced compared with those of TC18 alloy (1151 MPa, 0.6%). This phenomenon can be mainly attributed to the network microstructure, β grain refinement, and elevation of the proportion of α-colony brought about by the introduction of TiBw. However, with the further increase of TiBw volume fraction (above 1.0 vol%), the strength and the ductility of the composites were decreased. Consequently, the network microstructure strategy with minor reinforcement addition offers a pathway to design engineering composites overcoming the strength-ductility trade-off dilemma.