Interface evolution and synergistic strengthening-toughening induced by silicides in Ti-Al-Nb-Y composites

TiAl intermetallic alloys are limited in engineering applications by poor room-temperature ductility and wear resistance. In this work, the effects of Si content on microstructure and properties of Ti-45Al-8Nb-0.2Y- x Si composites prepared by spark plasma sintering are investigated. The morphology and distribution of precipitates at grain boundaries are controlled by Si content. Dispersed Y₂O₃ and Ti₅Si₃ particles are formed in situ at the interface of the lamellar colonies, which refine the grain size and promote the formation of equiaxed γ grains along the interface. It was found that the precipitate characteristics could be effectively tailored by the Si content: at 0.1 wt% Si, only dispersed Y₂O₃ particles were precipitated, whereas at 0.25 wt% Si, dual-phase precipitation of Y₂O₃ and Ti₅Si₃ occurred, leading to increases in compressive strength and fracture strain to 2421.2 MPa and 46.28%, respectively, together with a low wear rate of 1.25 × 10⁻⁴ mm³ (N m)⁻¹. Excessive Si induces Ti₅Si₃ agglomeration and coarsening of the interfacial structure, resulting in reduced properties. Appropriate Si addition achieves a synergistic strengthening-ductility effect, offering a new route to balance the strength, ductility, and wear resistance of TiAl composites.