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 alpha phase region to further improve the hightemperature 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 gamma 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 gamma matrix and follow a specific orientation relationship of (120)Y2O3// (111)gamma and [210]Y2O3// [110]gamma. 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-0.05Y(2)O(3) and Ti-48Al-6Nb-0.05Y(2)O(3) 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.