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 100-200MPa. 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.