C元素添加对近β钛合金显微组织及力学性能的影响

Effect of C Addition on Microstructure and Mechanical Properties of Near Beta Titanium Alloy

摘要:

研究了在不同热处理条件下C元素的添加量对近β钛合金Ti-4Al-5Mo-8V-2. 5Cr-1Sn-2Zr微观组织及力学性能的影响。结果表明:C元素添加对近β钛合金在不同热处理条件下的微观组织均有显著影响。C元素添加会导致β晶粒的细化,当C元素添加量由0%(体积分数,下同)增加到3%时,固溶处理后合金的β晶粒尺寸由137μm降低至25μm,且尺寸更加均匀。当C元素添加量持续增加时,β晶粒开始长大。经时效处理后,随着C元素添加量的增加,次生α相尺寸和体积分数均减小。相比于单级时效,双级时效呈现出更多的次生α相。此外,单级时效后晶界处的次生α相会随着C元素添加量的增加而逐渐消失。由于受晶粒细化、TiC颗粒和次生α相的影响,随着C元素添加量的增加,合金的显微硬度和拉伸强度明显提高,塑性降低。

关键词:近β钛合金;;TiC;;热处理;;组织演变;;显微硬度

Abstract:

The effects of trace carbon element on microstructure and mechanical properties of a near beta titanium alloy Ti-4Al-5Mo-8V-2. 5Cr-1Sn-2Zr through various heat treatment were studied. The results show that the addition of carbon element has a significant effect on the microstructure after different heat treatments. The addition of carbon leads to the refinement of beta grains. And after the solution treatment,the size of beta grains decrease from 137 μm to 25 μm and becomes more uniform with the increasing of carbon volume fraction from 0% to 3%. And beta grains begin to grow as the carbon content continues to increase. After aging treatment,the size and volume fraction of secondary alpha phase decreases with the increasing of carbon. Compared with the samples after single-aging treatment,the samples after double-aging treatment present the more secondary alpha phase. Additionally,with the increase of carbon,grain boundary alpha phase reduces gradually through single-aging treatment. Due to the influence of grain refinement,Ti C particles and secondary alpha phase,with the increase of carbon,the micro-hardness and tensile strength of the alloy increased significantly,but the ductility decreases.

Key words:near beta titanium alloy;TiC;heat treatment;microstructure evolution;micro-hardness