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

Near β Titanium Alloy with High Strength Obtained by Composition Design and Intermediate Annealing Process

摘要:

基于临界成分的多元合金化原则，结合电子浓度、钼当量和B_o-M_d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。利用光学显微镜、扫描电子显微镜、X射线衍射仪、背散射电子衍射和透射电子显微镜等技术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，由于马氏体具有阻碍晶界迁移的作用，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38 μm，晶粒细化使得退火处理后的合金具有良好的强塑性匹配，屈服强度达到1050 MPa，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，使合金强度突破1500 MPa并具有5%的延伸率。

Abstract:

A near β-type Ti-5.5V-4Mo-2.2Cr-Fe-3.6Al alloy was designed based on the multi-alloying principle of critical compo-sition, combined with parameters, such as electron concentration, molybdenum equivalent and B_o-M_d, that can influence the stability of β phase. The homogenized 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 by optical microscope, scanning electron microscope, X-ray diffractometer, electron backscattered diffraction and transmission electron microscope, as well as room-temperature tensile properties. The results show that martensitic transformation occurs in the alloy during rolling. The grain size of the alloy after intermediate annealing is only 38 μm, because the martensite is a hindrance to grain boundary migration. Grain refinement endows the annealed alloy with a good match of strength and plasticity, a yield strength of 1050 MPa and an elongation of 15%. 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 5%.