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.