Effects of Heat Treatment Process on Microstructure and Tensile Properties of Ti₂AlNb Alloy Forging

The effects of solution temperature and solution time on the microstructure and tensile properties at room temperature and 650 ℃ high temperature stretching for a case ring forging of Ti-22Al-25Nb alloy were studied. The relationships between the microstructure and tensile properties were also revealed. The results show that the bimodal microstructure is composed of the equiaxed α₂ particles, primary lath O phase and secondary acicular O phase. The prolongation of solution time has little effect on the microstructure. On the one hand, the increase of solution temperature will significantly reduce the content of primary lath O phase, and on the O ther hand, it will significantly increase the content of secondary acicular O phase precipitated during aging. The increase of secondary acicular O phase content reduces the mean free path of dislocation movement and increases the precipitation strengthening effect, which leads to the increase of strength of the alloy at room and high temperature, on the contrary, the plasticity decreases.