【作者】 李刚；

【导师】 黄安国；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2008， 硕士

【摘要】 钛金属在金属结构材料中仅次于铁、铝、镁,居第4位,被誉为发展中的第3金属材料。钛及其合金由于具有强度高、密度小、耐腐蚀、无磁、焊接性能好等一系列特点,一直受到世界各国的重视,发展迅速。近年来,钛在石油、化工、汽车、生物医学和文体用品等领域开始得到应用,并已成为新工艺、新技术、新设备不可缺少的金属材料。对于异种材料的连接,采用传统的熔焊方法很难实现可靠的连接,扩散连接作为固相连接方法之一,具有工艺简单、可操作性强、可连接大断面接头、零件变形小;连接接头质量好等优点。本文通过对TC4钛合金与Custom465不锈钢,TC4钛合金与25钢进行了相变超塑性扩散连接的可行性研究,利用扫描电镜、能谱仪、X射线衍射仪等方法对接头界面组织结构、物相组成等进行了较为系统的分析,研究钛合金与钢中元素扩散和金属间化合物形成的规律,在拉伸断裂机理分析的基础上,对钛合金与钢异种材料扩散连接的方式进行了对比分析。结果表明,通过对钛与不锈钢直接扩散连接接头研究发现,钛与不锈钢之间形成扩散层,Fe在钛合金侧发生了明显的扩散,界面相主要由FeC3、TiC、α-Fe、FeCr,β-Ti、FeTiO3等组成;对TC4/Ni/Custom465接头的研究表明,钛合金与镍中间层发生了强烈的互扩散,形成了明显的白亮扩散层,镍中间层两侧的Fe、Ti等元素的扩散没有穿透镍中间层,镍中间层的存在对两侧的Fe与Ti元素之间的互扩散起到了极为有效的阻隔作用。对比直接扩散连接接头,加入镍中间层后的接头焊合率有显著的提高,接头拉伸强度可达到348.45MPa。因此,合理的中间层对异种材料扩散连接接头有着重要的作用。对加Ni中间层的钛合金与25钢扩散连接接头扫描电镜分析发现,接头界面处形成了多层次的层状组织,结合接头能谱分析及X射线衍射分析表明在界面上存在NiTi2、NiTi、Ni3Ti、FeNi3、FeNi等多种金属间化合物;断口分析表明,在TC4钛合金侧有裂纹存在,断口为混合型,局部区域存在解理面和韧窝状的凹坑;对在高压力条件下无Ni中间层的钛合金与25钢扩散连接接头扫描电镜观察、能谱分析、X射线衍射分析,表明界面存在清晰的分界层,主要由α-Ti、Ni3Ti、Al3Ti、FeTiO3等物相组成。更多还原

【Abstract】 The titanium is regarded as the third development metal material, occupied 4th, next to accurately only aluminous, iron, magnesium in the metal. Because the titanium and the alloys have a series of characteristics such as the high intensity, the small density, anti-corrosive, no magnetism, well welding performance and so on, they are important received by the various countries continuously and develop rapidly. In recent years, titanium alloys have become essential metal material in the new technology, new technical and new equipment, applied in domains of petroleum, chemical, automobile, biomedicine, cultural and athletic equipment. For bonding of the heterogeneous materials, it is very difficult to realize the reliable connection used the traditional melt welding method. Diffusion bonding as one of solid phase bonding methods, has the simply craft, the easy operating, bonding of the big cross section attachment, slightly distorts of the components and well quality of joint and so on merits .Diffusion bonding of TC4 titanium alloy and the Custom 465 stainless steel, the TC4 titanium alloy and the 25 steel have been studied in the paper. Used the scanning electron microscope (SEM), Energy spectrometer and XRD and so on, the surface microstructures and the phase composition of bonding Joint have been systematic analysis. The law of the element diffusion and the intermetallic compound formed in titanium alloy and steel has also been studied. In the foundation analysis of the stretch failure mechanism, the way about diffusion bonding of the titanium alloy and the steel has been contrast analysisThe results indicated that in the direct diffusion bonding research of titanium and stainless steel the diffusion layer is formed between the titanium and the stainless steel, Fe has obviously diffused in titanium alloy and phase of the contact surface mainly contain FeC3, TiC, FeTiO3 and so on. Indicated to the research of TC4/Ni/Custom 465 joints, the intense mutual diffusion between titanium alloy and the Ni intermediate level has occurred and an obvious bright diffusion layer has formed. Diffusion of Fe, Ti has not penetrated the Ni intermediate level. The Ni intermediate level effectively impedes mutually diffusion of Fe and Ti in both sides. Contrasts the direct diffusion bonding, welding together ratio of joins with Ni intermediate level have the remarkable increased, and the tensile strength can reach 348.45MPa. Therefore, the reasonable intermediate level has the vital role to diffusion bonding the heterogeneous materials. Used SEM it discovered that the multi-level structures has been formed in the contact surface of diffusion bonding joins of titanium alloy and the 25 steel with Ni intermediate level. With Energy spectrometer analysis and XRD analysis indicated many kinds of intermetallic compounds such as NiTi2, NiTi, Ni3Ti, FeNi3, FeNi and so on exist in the contact surface. The fracture analysis indicated that there exist cracks in the TC4 titanium alloy side, and exist cleavage plane and the strong nest shape pit in the partial region. The fracture is the mixed type, explained the joins has certain toughness. Research of diffusion bonding joints of titanium alloy and the 25 steel under the high pressure condition the without Ni intermediate level used SEM, Energy spectrometer analysis, XRD analysis indicate that a clear zone exists in the contact surface and the phase mainly is composed of FeC3,α-Ti, Ni3Ti, Al3Ti, FeTiO3and so on.更多还原