热处理对近β锻造的多元Ti ₂ AlNb基合金组织和性能的影响

The new multi-compositional Ti ₂ AlNb alloy Ti-22Al-25Nb-1Mo-1V-1Zr-0.2Si was treated by the process of near β forging and heat treatments. The effects of heat treatments on the microstructure and mechanical properties were analyzed by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile test machine. The results show that the initial microstructure consists of the primary α ₂ phase, the needle like O phase and the matrix B2 phase. On the one hand, with the increase in solid solution temperature, the alloy strength is enhanced at room and high temperature, but the alloy ductility is reduced. On the other hand, with the increase in aging temperature, the variation of strength and ductility is completely opposite, compared to the increase in solid solution temperature. The primary alpha phase volume fraction (α ₂ /O) is mainly influenced by the solid solution treatment for the alloy. With the increasing of the solution temperature, the volume fraction of primary α ₂ /O alpha phase is reduced, enhancing the strengthening effect of needle like O phases. At the same time, the grain boundary pinning effect of the α ₂ to B2 phase is weakened, and then the growth of B2 grain decreases the plasticity. The morphology of precipitated phase is mainly affected by aging treatment. With the decrease in aging temperature, the thickness of precipitated fine O phase is decreased to enhance the strengthening effect of O phase, thus decreasing the volume fraction of B2 phase and the ductility of the alloy.