交变电场下不锈钢的电化学行为

主要研究了交变电场下SS304不锈钢在2.5 mol/L硫酸 溶液中的表面成膜情况.运用电位阶跃研究了不锈钢在交变电场高电位、低电位下的电化学 反应；用AFM准现场地观察了不锈钢在交变电场下各个阶段的成膜状况；用XPS分析了膜层的 纵向组成结构.结果表明：交变电场下不锈钢表面钝化膜的生长机制不同于直流钝化.最后 分析了不锈钢在交变电场下的电化学反应和成膜机理.     

Examination of superplastic forming combined with diffusion bonding for titanium: Perspective from experience

Superplastic forming (SPF) combined with diffusion bonding (DB) has been used successfully for the fabrication of titanium aerospace hardware. Many of these applications have been for military aircraft, whereby a complex built-up structure has been replaced with monolithic parts. Several methods for applying the two- and four-sheet titanium SPF/DB processes have been devised, including the welding of sheets prior to forming and the use of silk-screened stop-off (yttria) to prevent bonding where it is undesirable. Very little progress has been made in the past few years toward understanding and modeling the SPF/DB process using constitutive equations and data by laboratory testing. Concerns that engineers face in designing for fatigue life, acceptable design loads, and damage tolerance are currently being studied, but the database is very limited. This is a summary of past work found in the literature and forms the foundation for additional research. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

Infrared heat treatment of Ti-6Al-4V with electroplated Cu

The objective of this study is to investigate an innovative infrared (IR) technique to enhance adhesion of electroplated copper (Cu) on Ti-6Al-4V without dichromate dipping. The ultimate goal is to develop a Cu coating process on Ti-6Al-4V without hazardous hexavalent chromium (Cr) solution treatments. Cu coatings of around 50 μm were electroplated on Ti-6Al-4V specimens at a current density of 0.03 A/cm² in an acidic Cu solution. To improve adhesion of coatings, IR heat treatments were performed on the Cu-coated samples at different temperatures and durations: 860 °C for 600 s and 875 °C for 20–120 s. This process was accomplished in an attempt to replace the use of dichromate dipping before electroplating. For samples heat treated at 860 °C, no bonding existed, even after 600 s. It is believed that solid-state diffusion prevailed at 860 °C and that 600 s was not enough for sufficient diffusion to occur. Adhesion was poor when samples were heat treated at 875 °C for 20 s. Excellent adhesion was observed when the heat treatment holding time was increased to 40 s. For 90 s, the surface appearance of coatings partially changed from Cu-colored to a grayish color. There was no Cu left on the surface after a 120 s heat treatment. From optical microscopic observations on sample cross sections, an interlayer between the Cu and Ti-6Al-4V formed when heat treated at 875 °C for 40 s and longer. The interlayer thickness increased as the holding time increased, until depletion of Cu. The sheet resistivity of coated specimens was on the order of pure Cu for samples heat treated at 875 °C and less than 90 s. During the 875 °C heat treatment, the following occurred: solid-state diffusion of Cu in Ti-6Al-4V, formation of eutectic solutions, dissolution of Cu and Ti-6Al-4V into the liquid phase, and the formation of intermetallic compounds. The lowest eutectic temperature of 875 °C played a key role in this innovative process of Cu coating on Ti-6Al-4V. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana and appears on pp. 403–10 of the Proceedings.     

通过氢处理改善α＋β型钛合金的拉伸性能

提出了一种新的细化α+β型钛合金显微组织的氢处理工艺:在合金的氢化β转变点以下0—40K的温度范围对合金渗氢处理,空冷至室温,最后在948K真空除氢。Ti-6Al-4V和Ti-5Al-2.5Fe合金经此工艺处理后,组织显著细化,屈服强度,拉伸强度及延伸率分别提高8—15％,5—13％,7—14％。     

钛合金表面双层辉光离子渗铝的研究

利用双层辉光渗金属技术，以铝为源极、TC4(Ti-6Al-4V)为阴极、氩气为工作气体，依靠辉光放电和不等电位空心阴极效应在TC4表面形成合金层。采用X射线衍射和辉光放电光谱分析了合金层的相组成及渗层内Al元素的分布．并对其进行硬度测试。结果表明：渗层由Ti3Al和α-Ti组成；铝的含量可达18％；渗层厚度可达13μm；其硬度比经渗铝处理后的有了较大程度的提高。     

金属注射成形Ti-6Al-4V烧结坯的力学性能与烧结时间关系

研究了在1260℃烧结时,烧结时间对Ti-6Al-4V烧结坯力学性能的影响.结果表明平均晶粒尺寸为45 μm的氢化-脱氢粉末样品在1 260C烧结3 h～6 h,其相对密度为95.6%～96.7%、拉伸强度648 MPa～686 MPa、屈服强度526 MPa～615 MPa,但延伸率仅小于4%.90%气雾化(晶粒尺寸为32.5 μm)和10%氢化-脱氢混合粉末样品在1 260℃烧结2 h～6 h,其相对密度大于95%、拉伸强度800 MPa～848 MPa、屈服强度712 MPa～762 MPa、延伸率7.4%～9.5%.混合粉末样品的力学性能几乎达到美国ASTM粉末冶金的标准.     

W18Cr4V高速钢激光相变强化层的残余应力

利用Ｘ射线衍射法对Ｗ１８Ｃｒ４Ｖ高速钢激光相变强化层的残余应力进行了测定和分析。试验结果表明，相变强化层表面的残余应力为压应力，内部为拉应力，近似按正弦函数分布。其大小和分布状态随工艺参数的变化而改变。当改变工艺参数使表面熔化时，表面为拉应力。     

激光快速修复Ti-6Al-4V合金的显微组织与力学性能

针对Ti-6Al-4V合金在加工和服役过程中的损伤特点,对Ti-6Al-4V合金锻件的3种典型误加工缺陷——槽缺陷、面缺陷和体缺陷进行了激光快速修复研究。激光修复区与锻件基体形成致密冶金结合,Al、V合金元素由锻件基体到激光修复区均匀分布,无宏观偏析。激光修复区组织为粗大原始β晶粒内分布细长的α针及编织细密的α+β板条组织,呈现典型的魏氏结构,热影响区组织从锻件的等轴α+转变β组织逐步过渡到魏氏(α+β)组织。对预制有3种类型缺陷的激光修复试样进行室温静载拉伸试验和硬度测试,结果表明修复试样的拉伸性能达到锻件标准(HB5224-1982)。激光修复试样的硬度和强度高于锻件基体,而塑性则低于锻件基体。因此,激光修复区和锻件基体可看作是一种“强+弱”的组合,这与二者的显微组织是相对应的。     

立轧对中厚板断面形状的影响

基于中厚板在立轧轧边后板坯变形的物理模拟,分析了平辊立轧与倒棱轧制对中厚板断面形状的影响。平辊立轧可显著减小坯料侧面双鼓形及折叠,倒棱轧制可有效消除坯料侧面双鼓形。     

氮离子注入的Ti6Al4V表面分析

利用表面分析技术(AES,XPS,SIMS)研究了经氮离子注入的外科植入材料Ti6Al4V表面成分与键合态,用轮廓仪的测量结果计算了氮离子注入深度及注入氮离子的Ti6Al4V的刻蚀速率。考虑到该合金的基体效应,对AES的定量结果进行了修正。结果表明,注入到合金中的氮离子与合金中的Ti形成高硬度的TiN,N的分布近似为Gauss形式,注入总深度约为350nm,在距表面约140nm处氮量最大,N与Ti的浓度比可达1.1。