热处理对近β锻造的多元Ti2AlNb基合金组织和性能的影响

Effect of Heat Treatment on Microstructure and Mechanical Properties of Near-β Forged Ti2AlNb Based Alloy

摘要:

以近β锻造的多元Ti2AlNb基合金Ti-22Al-25Nb-1Mo-1V-1Zr-0.2Si（at %）为实验对象，采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）和万能拉伸试验机等测试手段研究了不同热处理对近β锻造Ti2AlNb基合金组织和力学性能的影响。结果表明：经近β锻造空冷后的组织由初生α2相、针状O相和基体B2相构成。随着固溶温度的升高，合金室温、高温强度升高，塑性降低。而随着时效温度的升高，合金的强度和塑性变化规律与固溶处理的规律正好相反。分析认为，固溶处理主要影响合金中初生α2/O相体积分数，随着固溶温度的升高，初生α2/O相体积分数减少，使得针状O相的强化作用增强，同时造成α2相对B2晶界钉扎减弱，B2晶粒长大塑性降低。时效处理主要影响析出相形态，随着时效温度的降低，合金中析出板条厚度减小，使得细小板条强化作用增加，而有利于塑性的B2相体积分数减少，导致合金塑性降低。

Abstract:

The new muti-compositional Ti2AlNb alloy Ti-22Al-25Nb-1Mo-1V-1Zr-0.2Si was treated by the process of near beta forging and heat treatment. The effect of heat treatment on the microstructure and mechanical properties were analyzed by means of the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile test machine. The results show that the initial microstructure contains the primary α2 phase, the needle like O phase and the matrix B2 phase. On the one hand, with the increasing of 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 increasing of aging temperature, the variation of strength and ductility is completely opposite, compared to the increasing of solid solution temperature. It is analyzed that the primary alpha phase volume fraction α2/O was mainly influenced by the solid solution treatment for the alloy. With the increasing of the solution temperature, the α2 /O primary alpha phase volume fraction is reduced, leading to the strengthening effect of needle like O phases enhanced. At the same time, the grain boundary pinning effect of the α2 phase to B2 is weaken, then the B2 grain growth cause the plasticity decrease. The morphology of precipitated phase is mainly affected by aging treatment. With the decreasing of aging temperature, the thickness of precipitated fine strip phase decrease, which makes the strengthening effect of fine strip increase, the volume fraction of B2 phase decrease, and the ductility of the alloy reduce.