High-pressure sintering of yttria-modified Ti-6Al-4V matrix composites with hierarchical network structures for enhanced high-temperature performance

Three-dimensional network-structured titanium matrix composites are promising for elevated-temperature applications, but their performance is often limited by grain coarsening and interfacial instability. In this work, Ti-6Al-4V matrix composites reinforced with in-situ TiB–TiC networks and trace Y 2 O 3 were fabricated by high-pressure high-temperature sintering at 5.5 GPa. The effects of sintering temperature and Y 2 O 3 addition on microstructure evolution, thermal stability, mechanical properties, high-temperature compression behavior, and cyclic oxidation resistance were investigated. At 1600 °C, the reaction between Ti64 and B 4 C led to the formation of a continuous TiB–TiC network along prior particle boundaries. The addition of 0.2 wt% Y 2 O 3 retained the network structure and refined the α–Ti matrix, decreasing the average grain size from 1.16 μm to 0.86 μm. The Y 2 O 3 -containing composite exhibited an ultimate compressive strength of 1771 MPa at room temperature and maintained a hardness of about 484 HV after annealing at 600 °C for 100 h. During high-temperature compression, it achieved a compressive stress of approximately 1098 MPa with 18.1% strain at 600 °C and sustained more than 45% strain at 800 °C without fracture. Cyclic oxidation tests showed that the Y 2 O 3 -containing composite had the lowest mass gain among the tested samples. Cross-sectional observations revealed a thinner oxide scale at 600 °C and retained Y–O-rich particles near the oxide/substrate region, suggesting improved local interfacial stability. These results demonstrate that combining a TiB–TiC network with trace Y 2 O 3 is an effective route to improve the high-temperature performance of Ti64-based composites.