Microstructure and Mechanical Properties of Ti-22Al-25Nb Alloy during Hot Mechanical Processing

The microstructure and mechanical properties of Ti-22Al-25Nb alloy was investigated and the effects of the forging, solution and aging temperature on the mechanical properties were discussed. Results show that as the isothermal forging temperature increases, the strength and ductility of the alloy increase at first and then decrease. When the solution is conducted in O+B2 region, as the solution temperature increases, the increasing B2 volume and decreasing particle amount are the main reason for high ductility of the alloy. When the solution is conducted in α₂+B2+O region, the decrease of lamellar thickness is beneficial for the strength increasing while the large B2 grain size and fine lamella are harmful for the ductility. The phase volume, morphology and size have a significant influence on the mechanical properties of the alloy. A basic principle to improve the tensile property of the alloy is isothermal forging nearby the B2-transus in order to control the amount of the particles and the B2 grain size, and the subsequent aging is at low temperature to obtain fine lamella.