热处理温度对Ti-6Al-7Nb合金组织与性能的影响

Effect of Heat Treatment Temperature on Microstructure and Mechanical Properties of Ti-6Al-7Nb Alloy

为揭示Ti-6Al-7Nb合金显微组织、力学性能及相组成随热处理温度的变化规律,研究了合金在650~1 030℃热处理空冷条件下的组织演变,并进行了室温力学性能测试与XRD分析。结果表明:对于Ti-6Al-7Nb合金,经650℃热处理后,热加工得到的原β转变组织中析出了细小的α相,合金的强度和弹性模量有所提高。在700~850℃之间进行热处理,可以获得良好的综合性能,满足医用钛合金相关标准要求。在950~1 030℃范围内,随着热处理温度的升高,析出二次针状α相或生成α’马氏体相,呈现强度上升、塑性下降的趋势。经650、850℃热处理后,XRD图谱中均为α相的衍射峰,未出现β相的衍射峰。1 030℃热处理后,α’相具有较强的(002)、(101)衍射峰,其他晶面的衍射峰强度很弱,合金弹性模量可达108 GPa。

In order to reveal the variation of microstructure,mechanical properties and phase constitution of Ti-6Al-7Nb alloy with different heat treatment temperatures,the microstructure evolution of Ti-6Al-7Nb alloy was studied at 650 ~ 1 030 ℃ under air-cooled conditions,and the room temperature mechanical properties and XRD of the samples were tested. The results show that tiny alpha phases are precipitated in the original beta transformation structure of Ti-6Al-7Nb alloy after 650 ℃ heat treatment,and the strength and elastic modulus of the alloy are improved. In the range of 700 ~ 850 ℃,the alloy can obtain the good comprehensive performance,and meet the requirement of medical standards. With the increase of temperature in 950 ~ 1 030 ℃,due to the precipitation of secondary acicular alpha phase or the generation of the cubic martensite phase,the strength is increased,along with the plastic declined. At the two temperature points of 650 ℃ and 850 ℃,the XRD spectra of Ti-6Al-7Nb alloy are diffraction peaks of alpha phase without that of beta phase. After heat treatment at 1 030 ℃,the cubic martensite phase has strong( 002) and( 101)diffraction peaks,and the intensity of other lattice orientations is very weak. The elastic modulus of the alloy can reach108 GPa.