Microstructure and Mechanical Properties of the Isothermally Forged Ti-22Al-25Nb (at%) Alloy

The microstructure evolution and mechanical property of Ti-22Al-25Nb (at%) alloy by different phase region isothermal forging and heat treatment were studied. The results indicate that as the isothermally forging temperature increases from 980 degrees C (alpha(2)+O+B2 three phase region) to 1040 degrees C (alpha(2)+B2 two phase region) to 1060 degrees C (B2 phase region), the microstructures of alloys are equiaxed microstructure, duplex microstructure, and bimodal size lamellar 0 microstructure. The size and volume fraction of each phase can be controlled by heat-treatment schedule. The mechanical properties of alloys show that bimodal size lamellar 0 microstructure has the highest strength but the worst ductility; however, the equiaxed microstructure has the highest ductility but the lowest strength. The equiaxed microstructure has the worst creep resistance, while the duplex microstructure and the bimodal size lamellar 0 microstructure have similar creep resistance, because they are both mainly lamellar structure, which possess better creep resistance than the equiaxed microstructure.