Significant improvement in high-temperature mechanical properties of Y₂O₃-reinforced TiAl alloys by heat treatment

In this study, a simple heat treatment was conducted in the single α phase region to further improve the high-temperature mechanical properties of as-cast Y₂O₃-reinforced TiAl alloys. The heat-treated alloys exhibit a significant presence of Y₂O₃ nanoparticles precipitating along dislocations or twin boundaries in the γ phase. This is because the solid solution Y element is present in a supersaturated state in the solidified microstructure. The nanoscale precipitates form a strong interfacial bonding with the γ matrix and follow a specific orientation relationship of (120)Y₂O₃// (111‾)γ and [21‾0]Y₂O₃// [11‾0]γ. The heat-treated Y₂O₃-reinforced TiAl alloys demonstrate a substantial improvement in high-temperature mechanical properties, particularly in creep resistance. The creep life of Ti–48Al–2Cr–2Nb-0.05Y₂O₃ and Ti–48Al–6Nb-0.05Y₂O₃ alloy tested at 800 °C and 325 MPa increases by approximately 65.5 % and 99.4 % respectively. This enhanced creep resistance can be mainly attributed to the formation of Y₂O₃ nanoparticles and the increased volume fraction of lamellar colonies, which effectively hinder dislocation movement during creep. The heat-treated high-Nb TiAl alloy exhibits a greater increase in creep life primarily due to the reduced segregation.