通过成分设计和轧程中间退火工艺获得高强度近β型钛合金的研究

Research on the near β titanium alloy with high strength obtained by composition design and inter-mediate annealing process

摘要:

本文基于临界成分的多元合金化原则,结合电子浓度(VEC)、钼当量([Mo]eq) 和Bo-Md等衡量β相稳定性的参数设计了一种近β型Ti-5.5V-4Mo-2.2Cr-Fe-3.6Al合金。对均匀化处理后的试样进行轧程中间退火处理,最后对合金进行时效处理。光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、背散射电子衍射(EBSD)和透射电子显微镜(TEM)等技术用于分析合金在不同状态下的组织,同时对合金的室温拉伸性能进行测试。结果表明,在轧制过程中合金发生马氏体相变,由于马氏体阻碍晶界的迁移的作用,经过轧程中间退火后的合金获得了极其细小的晶粒组织。中间退火后合金的晶粒度为38μm,晶粒细化使得经过退火处理后的合金具有良好的强塑性匹配,拉伸屈服强度达到1100MPa同时延伸率达到15%。经过时效处理后合金的组织中析出了大量细小而弥散的α相,细小α相的析出进一步提高了合金的性能,使合金的强度突破1500MPa并具有4%以上的延伸率。

Abstract:

In this work, a near β-type Ti-5.5V-4Mo-2.2Cr-Fe-3.6Al alloy was designed based on the multi-alloying principle of critical molybdenum equivalent ([Mo]eq), combined with parameters such as electron concentration (VEC), Bo-Md that can influence the stability of β phase. The alloy was subjected to solid solution, intermediate annealing during the rolling process, and aging treatment. The microstructure and mechanical properties of the alloy were analyzed. The results showed that martensitic transformation occurs in the alloy during rolling. The grain size of the alloy after annealing during the rolling process is only 38 μm, due to the martensite has a hindrance to grain boundary migration. Then it has good strength-plasticity matching, the tensile yield strength reaches 1150 MPa and the elongation is more than 10%. A large number of α phases are precipitated in the microstructure of the rolled alloy after aging treatment, which further improves the properties of the alloy. The strength of the alloy exceeds 1500 MPa and the elongation is more than 5 %.