A novel Ta-contained TiAl alloy with excellent high temperature performance designed for powder hot isostatic pressing.

TiAl alloys offer strong potential for replacing conventional nickel-base alloys in structural applications at high temperatures, which requires good high temperature performance. This study analyzes the creep performance and thermal exposure characteristics for a powder hot isostatic pressing (P-HIP) Ta-contained TiAl alloy. The microstructure characteristics, creep performance, and thermal exposure properties of the nearly lamellar (NL) alloy with a size of about 145 μm were investigated. The alloy remains 0.72 % fracture strain at room temperature after exposure at 750 ℃ for 1000 h. The fitting results of creep curves show that the creep stress index n is 15.82 at 750 ℃, indicating the power law creep mechanism. By reducing the interfacial energy, Ta can facilitate the formation of metastable structures and achieve refinement. The enrichment of Ta element at the lamellar edge, both observed after thermal exposure and creep, inhibits the growth of lamellae and hinders the expansion of cavities due to its low diffusion rate, improving the thermal stabilities and creep performance. The P-HIP Ta-contained TiAl alloy shows exciting high temperature performance. • A powder metallurgy Ti–48Al–3Nb–1.5Ta alloy with excellent high temperature performance is obtained with simple heat treatment process. • The mechanism of Ta for this alloy to improving the thermal stabilities and creep performance is revealed. The enrichment of Ta element at the lamellae edge has an effect of inhibiting the growth of lamellae and hindering the expansion of pores. • The fitting results of creep curves show that the creep stress index n is 15.82 at 750 ℃, indicating power law creep mechanism. • After exposure at 750 ℃ for 1000 h, the lamellae have no obvious coarsening and the material still has 0.72 % tensile fracture strain at room temperature, indicating favorable microstructure stability and mechanical performance. [ABSTRACT FROM AUTHOR]