Simultaneous enhancement of strength and plasticity in YSi₂/Ti-45Al-8Nb composites prepared by SPS technology: The role of YSi₂ precursor

This study proposes a novel approach by incorporating YSi₂ precursor into Ti-45Al-8Nb alloy by spark plasma sintering (SPS). During SPS processing at 1300 °C, YSi₂ decomposes controllably and undergoes in-situ reactions: Y reacts with internal oxygen to form finely dispersed Y₂O₃ particles, while Si dissolves into the matrix or precipitates as Ti₅Si₃. The Y₂O₃ particles pin grain boundaries, reducing the average lamellar colony size. The contribution of the Si element enables abundant dislocations and even twins to be stored in the γ lamellae. With the addition of 0.3 wt% YSi₂, the high-temperature tensile strength of the composite reaches 448 MPa, which is 24.8% higher than that of the initial alloy. The compressive strength reaches 2239.2 MPa, and the fracture strain is 38.4%, representing improvements of 32.6% and 25.1%, respectively, over the initial alloy. These values are significantly higher than those of many recently reported SPS-processed TiAl composites. The enhancement is attributed to multiple mechanisms: grain refinement governed by Y₂O₃, solid-solution strengthening from Si, precipitation hardening by Ti₅Si₃, and the stacking fault/twinning effect in the γ lamellae. This work demonstrates that compound doping via SPS technology offers a viable strategy for optimizing the mechanical properties of high-performance TiAl composites.