Elevated temperature performance and creep behavior of Y₂O₃ reinforced Ti-48Al-6Nb alloy at the brittle-ductile transition temperature

This study investigated the elevated temperature properties and creep behavior of Y₂O₃-bearing Ti-48Al-6Nb alloy. Tensile and creep tests of Ti-48Al-6Nb and Ti-48Al-6Nb-0.05Y₂O₃ alloys were performed. The results show that the brittle-ductile transition temperatures (BDTTs) of both alloys are determined to be 825–850 ℃ by tensile tests at the strain rate of 5 × 10⁻⁴ s⁻¹. And the BDTTs of both alloys are determined to be 800–825 ℃ by creep tests under a constant stress of 325 MPa, reducing about 25 ℃ due to the slower creep rates. Y₂O₃ improves the creep properties of the alloys by refining α₂/γ lamellar spacing, decreasing segregation and preventing dislocation movement. Furthermore, creep deformation behavior of α₂ phases at the BDTT was discussed. Deformation of α₂ laths during creep is mainly provided by a→ type dislocations below the BDTT. While above the BDTT, 2c→+a→ type dislocations were activated due to the active thermal activation and decreasing Peierls-Nabarro stress. The presence of 2c→+a→ slip systems in α₂ laths contributes to ductile deformation during creep.