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

TiAl 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-Al-Nb-Y-xSi 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 ceramic 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. When the Si content is 0.25 wt.%, the compressive strength and fracture strain increase to 2421.2 MPa and 46.28%, and the wear rate is as low as 1.25 × 10-4 mm3·(N·m)-1. Excessive Si causes Ti5Si3 agglomeration and interface structure coarsening, resulting in reduced properties. Appropriate Si addition realizes synergistic strengthening-toughening, offering a new route to balance strength, ductility, and wear resistance of TiAl composites.