Microstructural evolution, creep, and tensile behavior of a Ti-22Al-25Nb (at%) orthorhombic alloy

The microstructure, creep, and tensile deformation behavior of a Ti-22Al-25Nb (at%) alloy were studied. The ring-rolled materials were produced through conventional thermo-mechanical processing techniques comprising nonisothermal forging and rolling. Heat treatments at all temperatures above 1060 °C, followed by water quenching, resulted in fully-B2 microstructures. Above 980 °C, the equiaxed O phase was shown within the B2 grains, while lamellar O-phase precipitated below 980 °C. Tensile-creep experiments were conducted in the temperature range 600-700 °C and stress range 100-200 MPa. The measured creep exponents and activation energies suggested that the creep mechanisms were dependent on stress and microstructure. The tensile strength of the alloy at room temperature and 650 °C was also investigated. Microstructural effects on the tensile properties and creep behavior were also discussed and the data were compared to that for other Ti2AlNb-based alloys.