Simultaneously enhancing room-temperature strength-ductility synergy and high-temperature performance of titanium matrix composites via building a unique bimodal architecture with multi-scale reinforcements

To meeting the double demands of structural weight reduction and performance improvement of aerospace vehicle, conventional high-temperature titanium alloys or titanium matrix composites (TMCs) are encountering a huge challenge that the room-temperature ductility will be inevitably deteriorated in pursuit of enhancing the elevated high-temperature strength. The present work proposes a feasible strategy for resolving this contradiction by constructing a novel bimodal architecture and introducing the multiscale reinforcements of microsized TiB whiskers and micro/nanosized Y₂O₃ particles. The unique bimodal microstructure consists of primary microsized α_p/β lath clusters and micro/nano basketweave-like structure composing of α_p, secondary nanosized α_s and β laths. It is noteworthy that the bimodal (TiB+Y₂O₃)/Ti composite exhibits excellent mechanical properties with the ultimate tensile strength (UTS) of 1318 MPa with the total elongation to failure (EL) of 10.5 % at room temperature, and UTS of 934 MPa with EL of 23 % at 600 °C, far higher that of the reported 600 °C high temperature titanium alloys or TMCs. In-situ investigations indicate the postponed strain localization, the activated extra 〈c + a〉 dislocations within α_p laths, and the heterogeneous deformation induced (HDI) hardening caused by the unique bimodal microstructure, synergistically promoted the ductility of bimodal (TiB+Y₂O₃)/Ti composite. While the strength enhancement at room temperature and 600 °C is attributed to the synergistic strengthening effect of nanosized α_s, microsized TiB whiskers and micro/nanosized Y₂O₃ particles and HDI strengthening. These findings provide a new insight for improving mechanical properties of metal matrix composites.