Ti-6Al-7Nb合金随温度的组织与性能演变

Microstructures and mechanical properties evolution of Ti-6Al-7Nb alloy with temperatures

摘要:

为揭示Ti-6Al-7Nb合金随热处理温度的不同,显微组织、力学性能及相组成的变化规律,研究了合金在650℃-1030℃热处理空冷条件下的组织演变,进行室温力学性能测试与XRD分析。结果表明：650℃属于时效温度,热加工得到的原β转变组织中析出细小的α相,合金的强度和弹性模量有所提高。700℃-850℃之间进行热处理,可以获得良好的综合性能,满足相关标准要求。合金弹性模量处于94-100 GPa。950℃-1030℃温度范围内,随着温度的升高,由于二次针状α相的析出,或者生成α"相,呈现强度上升,塑性下降的趋势。650℃、850℃两个温度热处理后,Ti-6Al-7Nb合金的XRD图谱未出现β相的衍射峰,均为α相的衍射峰。1030℃热处理后,α"相具有较强的(002)、(101)衍射峰,其它晶面的衍射峰能量很弱。合金弹性模量达最大值108GPa。通过金相观察,推算Ti-6Al-7Nb合金α+β→β转变的开始温度处于900℃-920℃,终了温度处于1010℃-1030℃。

Abstract:

In order to reveal the variation of microstructure, mechanical properties and phase composition of Ti-6Al-7Nb alloy with different heat treatment temperatures, the microstructure evolution of Ti-6Al-7Nb alloy was studied at 650°C -1030°C under air-cooled conditions, and the room temperature mechanical properties and XRD of the samples were tested. The results show that 650℃ belongs to the aging temperature of the alloy. The beta transition structure obtained by hot working precipitates tiny alpha phase, with strength and elastic modulus increased. In the range of 700°C-850°C, the alloy can obtain the good comprehensive performance, and meet the requirement of related standards. The elastic modulus of the alloy is 94-100Gpa. With the increase of temperature in 950℃-1030℃, due to the precipitation of secondary acicular alpha phase or the generation of the cubic martensite phase, the strength is rised, along with the plastic declined. At the two temperature points of 650℃ and 850℃, the XRD spectras of Ti-6Al-7Nb alloy are diffraction peaks of alpha phase without that of beta phase. After the heat treatment of 1030℃, the cubic martensite phase has strong (002) and (101) diffraction peaks, and the energy of other lattice orientations is very weak. The elastic modulus of the alloy reaches a maximum of 108 GPa. Through metallographic observation, the start temperature of α+β→β transformation is in 900℃-920℃, and the end temperature of that is in 1010℃-1030℃.