钛合金循环置氢组织与性能研究

发布时间：2017-12-28 19:16

本文关键词：钛合金循环置氢组织与性能研究　出处：《合肥工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：钛合金具有比强度大、耐腐蚀性好、高温性能可靠等优点,在航空航天领域得到广泛的应用。但是钛合金室温塑性差,变形抗力较大,制约了其冷态成形的发展。因此绝大部分钛合金需要在高温下成形,对模具和成形设备要求较高,加大了制造成本,限制了钛合金的应用。钛合金的热氢处理技术,把氢当作临时合金化元素,借助氢致相变、氢致塑性、可逆合金化等特性来改变钛合金的热加工性能。但是热氢处理技术主要集中于单一道次的置氢处理,而关于多道次的循环热氢处理研究在国内外尚属空白。本文对Ti6Al4V合金进行多道次循环置氢处理,利用金相显微镜、X射线衍射仪、热重分析仪等手段,结合室温压缩试验,对循环热氢钛合金的显微组织和力学性能进行了系统研究。利用M-200型摩擦磨损试验机对不同氢含量的Ti6Al4V合金进行摩擦磨损试验,以研究氢含量对钛合金摩擦磨损性能的影响规律。采用第一性原理方法构建了不同氢浓度的aTi-H晶体体系,研究了不同氢含量下,aTi-H体系的结构、能量、能带结构、电子态密度的变化规律。试验结果表明：一道次置氢钛合金极限变形率增加了17.67%,室温塑性的增强得益于钛合金内β相的增多。而多道次循环置氢导致钛合金发生氢脆,促进了组织内氢化物的生成,并且伴随着置氢次数的增加,针状α马氏体的数量减少,α”马氏体增多。压缩后的循环置氢试样晶粒弯曲并得到一定程度细化,α”体积分数增大,未发现剪切带的形成。氢使钛合金的摩擦系数降低,但是氢含量对Ti6Al4V合金摩擦系数的影响不明显。随氢含量的增加,钛合金的耐磨性能逐渐变差。随着氢含量的增加,钛合金的氧化磨损特征逐渐变弱,磨粒磨损所起的作用逐渐增强。Ti-H晶胞的体积和体积膨胀率随着氢含量的升高而增大,发生了晶格畸变,晶胞结构不稳定,更易生成钛氢化合物。晶胞的稳态能量和杂质形成能随着氢含量的增大而减小。纯Ti晶体的能带结构图表现出典型的金属导体能带特质,能带在费米能级的周围密集分布,具有典型的金属性。置氢后钛原子之间的部分成键力降低,存在弱键效应。
[Abstract]:Titanium alloy has many advantages, such as large specific strength, good corrosion resistance, reliable high temperature performance and so on. It has been widely used in the field of aerospace. However, the plasticity of the titanium alloy at room temperature is poor and the deformation resistance is large, which restricts the development of cold forming. Therefore, most of the titanium alloy needs to be formed at high temperature, higher requirements for mould and forming equipment, increased manufacturing cost, and restricted the application of titanium alloy. The hot hydrogen treatment technology of titanium alloy takes hydrogen as a temporary alloying element, and changes the hot working property of titanium alloy by virtue of hydrogen transformation, hydrogen induced plasticity and reversible alloying. However, the thermal hydrogen treatment technology is mainly concentrated on the single channel hydrogen treatment, and the study of multipass cyclic hydrogen treatment is still blank at home and abroad. In this paper, Ti6Al4V alloy was treated by multi pass cycle hydrogen treatment. The microstructure and mechanical properties of the recycled hot hydrogen titanium alloy were systematically studied by means of metallographic microscope, X ray diffractometer, thermogravimetric analyzer and room temperature compression test. The friction and wear tests of Ti6Al4V alloy with different hydrogen content were carried out by using M-200 friction and wear tester to study the effect of hydrogen content on the friction and wear properties of titanium alloy. The aTi-H crystal system with different hydrogen concentration was constructed by first principles method. The structure, energy, band structure and electronic state density of aTi-H system under different hydrogen content were studied. The experimental results show that the ultimate deformation rate of a secondary hydrogen titanium alloy increases by 17.67%, and the increase of the plastic properties at room temperature is due to the increase of the beta phase in the titanium alloy. However, the hydrogen embrittlement of titanium alloy is promoted by multipass cycle hydrogenation, and the formation of hydrides is promoted. With the increase of hydrogenation times, the number of needle like alpha martensite decreases and the "alpha" martensite increases. The grain size of the specimen after compression is refined to a certain extent, and the volume fraction of alpha increases, and the formation of the shear band is not found. The friction coefficient of the titanium alloy is reduced by hydrogen, but the effect of hydrogen content on the friction coefficient of Ti6Al4V alloy is not obvious. With the increase of hydrogen content, the wear resistance of the titanium alloy gradually decreases. With the increase of hydrogen content, the oxidation wear characteristics of the titanium alloy gradually become weaker, and the effect of abrasive wear is gradually enhanced. The volume and volume expansion rate of the Ti-H cell increases with the increase of hydrogen content, and the lattice distortion occurs, the structure of the cell is unstable, and the titanium hydride is more easily generated. The steady state energy and impurity formation energy of the cell decrease with the increase of hydrogen content. The band structure diagram of pure Ti crystal shows typical metal conductor band characteristics, which can be closely distributed around the Fermi level and has typical metallicity. The bonding force between the titanium atoms is reduced and the weak bond effect exists after hydrogen placement.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.23

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