工艺参数对2A12铝合金微弧氧化陶瓷层生长的影响

研究了正／负向电流密度、频率和正／负向占空比对铝合金微弧氧化陶瓷层生长的影响,采用扫描电子显微镜（SEM）和X射线衍射仪（XRD）,分析了不同氧化时间陶瓷层表面和截面形貌、成分和相组成,讨论了陶瓷层的生长过程。研究表明,正／负向电流密度相同时,随电流密度的增加膜层厚度增大;而当正向电流密度相同时,负向电流密度增加有利于膜层的生长;成膜速率随脉冲频率和负向占空比增加,均呈现先增大后减小的趋势;陶瓷层总厚度随氧化时间接近于线性增长,致密层占总膜层的比例先快速增加,其后略微下降。SEM结果显示,随氧化时间延长,样品表面膜厚度趋于均匀,界面处氧化膜变得比较平坦。陶瓷层主要由α—Al2O3和γ-Al2O3相组成,随氧化时间的延长,γ-Al2O3相在陶瓷层中的相对含量逐渐减少。而α-Al2O3相的含量逐渐提高。     

氢氧化钠浓度对镁合金阳极氧化的影响

采用电压-时间曲线、全浸腐蚀实验、极化曲线法、X射线衍射法(XRD)、扫描电镜(SEM)和能量色散谱仪(EDS)等方法研究了AZ91D镁合金在含不同浓度氢氧化钠溶液中的阳极氧化行为和膜层的成分、结构。结果表明,在本研究给定工艺中,AZ91D镁合金的阳极氧化过程可分为三个阶段:电火花出现之前的致密层生成阶段,少量小电火花出现的多孔层生成阶段,出现较大电火花的多孔膜层稳定生长阶段。阳极氧化过程中,随着NaOH浓度的升高,出现电火花的时间缩短,出现电火花的电压值降低,阳极氧化膜表面的颗粒变小、孔隙率减小,膜层厚度减小;阳极氧化膜的主要组成是MgO,并含有少量的Mg3B2O6;NaOH浓度对阳极氧化膜耐蚀性影响较大,当NaOH浓度为40g/L时,膜层的耐蚀性能最好。     

铝合金锻件阳极氧化膜发黑缺陷控制技术研究

研究了LC9CGS3铝合金锻件硫酸阳极氧化膜颜色发黑缺陷的控制技术.采用光学显微镜(OM)、扫描电子显微镜(SEM)和能谱分析仪(EDS)等分析技术,研究了LC9CGS3铝合金锻件硫酸阳极氧化膜颜色发黑缺陷的形成机理.结果表明,造成阳极氧化膜颜色发黑的原因是由于热处理不当.通过工艺试验分析,获得了再现阳极氧化膜颜色发黑缺陷的方法；通过加工流程的再造,获得了缺陷控制的技术；通过缺陷控制,大幅度地提高了产品的合格率.     

钛合金稀土阳极化成膜过程的电化学研究

 对钛合金稀土阳极氧化的电化学过程进行了研究;重点研究了钛合金稀土阳极氧化的成膜过程;分析了不同硫酸浓度,不同成膜电压条件下,电化学参数的变化,讨论了稀土阳极氧化膜的形成机理;通过对阳极氧化膜的 SEM微观形貌图及其他电化学参数的分析,推断氧化膜为分层结构;在一定温度和电压下,对电极电位的变化进行了研究,探讨了稀土阳极氧化膜的形成过程和导电机制;提出了稀土阳极氧化膜是由具有一定半导体特性和电容性的致密层与多孔层构成的,整个成膜过程中导电是由空穴、铈盐离子和溶液离子共同完成的。     

5A05铝合金黑色氧化膜的结构及耐蚀性能

用两步化学氧化法在铝合金表面获得了黑色氧化膜。利用全浸渍腐蚀试验及电化学极化曲线评价了膜的耐蚀性能,利用扫描电子显微镜观察膜的表面形貌,采用能量散射谱(EDS)测定膜的成分。结果表明:铝合金的黑色氧化膜具有网块状结构,膜层主要由O、Al、Mn、Co、Cr五种元素所组成,未经封闭的铝合金氧化膜的耐蚀性能很差,而经重铬酸钾封闭后,耐蚀性大为提高。     

阳极氧化膜厚度对TB8钛合金表面特性及其粘结性能的影响

采用以酒石酸钠为主盐的电解体系对TB8钛合金进行阳极氧化,研究阳极氧化膜厚度对TB8钛合金表面特性及其与环氧树脂粘结性能的影响。采用SEM、XRD和EDS分析了阳极氧化膜的微观形貌和晶体结构,采用角接触测量仪和三维视频显微镜分别对阳极氧化膜的表面润湿性和粗糙度进行测量。研究了不同厚度TB8钛合金阳极氧化膜的粘结性能与表面形貌、相组成、润湿性及粗糙度的关系。结果表明:采用以酒石酸钠为主盐的电解体系对TB8钛合金进行阳极氧化处理,氧化时间为15 min,电压为1~30 V时,能够在钛合金表面形成一层1~4μm厚的阳极氧化膜;氧化膜主要由金红石型和锐钛型TiO₂混合晶体组成,其表面具有微纳多孔的粗糙结构;随着厚度的增加,阳极氧化膜对水的润湿性能逐渐增强。当氧化膜厚度为3μm时,可获得最大粘结强度为19.6 MPa,相对于母材提高了88.5%,同时,水接触角为43.2°,相对于其母材减少了56.1%;粗糙度为2.14μm,相对于母材提高了137.8%。     

基于移动粒子半隐式方法的旋流液膜破碎过程模拟

为实现旋流初始雾化中液膜破碎过程的直接数值模拟,基于GPU (Graphics processing unit)加速和移动粒子半隐式方法 (Moving particle semi-implicit method, MPS),开发了离心式喷嘴液膜破碎过程的并行加速数值模拟方法与程序,模拟了喷雾场三维形态特征和初始雾化破碎过程。模拟结果成功捕捉到了液膜形成、液膜破碎成液丝继而破碎成液滴的瞬态过程。模拟得到的雾化破碎过程与实验拍摄结果基本吻合。模拟了不同射流速度下的旋流液膜破碎过程,模拟得到的液膜初始破碎长度与经验公式计算结果趋势一致,二者吻合较好,最大误差为24.2%,模拟得到的液膜半锥角与实验值较为吻合,误差为10.6%。表明开发的模拟方法与程序的准确性,为后续离心式喷嘴的液膜雾化过程及雾化特性研究打下基础。     

SiB4 微粉在化学气相渗透SiC 过程中的变化

采用SEM、EDS、XRD分析了SiB4微粉化学气相渗透(CVI)SiC后的组成和结构,并用热力学计算研究了SiB4微粉在CVI SiC过程中变化的原因。结果表明:在CVI SiC过程中SiB4微粉不发生分解,但在近表层处氧化生成SiO2和B2O3。用SiB4浆料浸渍结合CVI工艺对C/SiC基体进行自愈合改性时,难以形成均匀致密的基体。     

Ground-based Investigations of Atomic Oxygen Erosion Behaviors of Silver and Ion-implanted Silver

Silver foils and ion-implanted silver foils exposed to atomic oxygen (AO) generated in a ground simulation facility were investi-gated by the quartz crystal microbalance (QCM), the scanning electron microscopy (SEM) and the X-ray photoelectron spectroscopy (XPS). The experimental results show the presence of Ag2O and AgO in an oxidation process of the silver foil having exposure to AO. As soon as silver comes under the bombardment of atomic oxygen, the oxidation process starts with a thick film forming on the silver surface. Because of the development of stresses, the oxide layer gets cracked and spalled, which leads to appearance of a new silver surface intensifying further oxidation. At last, AgO begins to form on the outer surface of the oxide film. The analytical results of the XPS and the AES attest to formation of a continuous high-quality protective oxide-based layer on the surface of ion-implanted silver films after exposure to AO. This layer can well protect materials in question from erosion.     

温度对溶剂热改性C/C复合材料显微结构和氧化性能的影响

以硼酸三正丁酯、乙酸、B2O3粉体为原料,无水乙醇为溶剂,采用一种新颖的溶胶/凝胶结合溶剂热法对C/C复合材料基体进行了抗氧化改性.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能量色散谱仪(EDS)及X射线光电子能谱(XPS)对改性后试样进行了表征.重点研究了溶剂热反应温度对改性后试样的物相组成、微观结构和氧化性能的影响.结果表明:经过溶剂热改性处理后,C/C复合材料表面缺陷被玻璃相B2O3组成的涂层所覆盖,材料内部一部分孔隙也被B2O3相填充,且随着溶剂热温度的上升,试样表面的微裂纹逐渐消失,B2O3涂层的致密度上升;C/C基体的抗氧化性能随着溶剂热改性温度(范围353～433 K)的升高而提高;经433 K溶剂热改性后的C/C复合材料在873 K的空气中氧化16 h后的质量损失仅为4.09％.     

Influences of pulse frequency on formation and properties of composite anodic oxide films on Ti-10V-2Fe-3Al alloy

A thick composite anodic oxide film was fabricated in an environmentally friendly malic acid electrolyte containing PolyTetraFluoroEthylene (PTFE) nanoparticles on Ti-10V-2Fe-3Al alloys. The influence of pulse frequency on the morphology, microstructure and composition of composite anodic oxide films containing PTFE nanoparticles was investigated using Field Emission Scanning Electron Microscopy (FE-SEM) equipped with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM) and Raman spectroscopy. The tribological properties in terms of the friction coefficient, wear loss and morphology of worn surfaces were measured by ball-on-disc tests. The electrochemical property was evaluated by potentiodynamic polarization. The results indicated that the titanium dioxide of composite anodic oxide films transformed from anatase to rutile with the change of pulse frequency, which could result from the electrochemical dynamic equilibrium. The combination of PTFE nanoparticles and malic acid electrolyte molecules can influence the energy fluctuation of electrochemical equilibrium and formation of composite anodic oxide films. Moreover, composite anodic oxide films fabricated under the condition of 1.0–2.0 Hz exhibited the best wear resistance and corrosion property. The schematic diagram of the film formation and PTFE nanoparticles spreading process under different frequencies was elucidated.     

周期换向脉冲法快速电沉积 Al2 O3／Ni 复合镀层

以 Al2 O3微粒为分散相,进行了周期换向脉冲复合电沉积工艺研究,快速电沉积出了 Al2 O3／Ni 复合镀层。利用扫描电镜及能谱分析技术对 Al2 O3／Ni 复合镀层的微观形貌及组成进行了表征,考察了脉冲参数对复合镀层中Al2 O3含量及镀层微观形貌的影响;并就周期换向脉冲电沉积与直流电沉积复合镀层的微观形貌、镀层应力及沉积速率进行比较。结果表明：采用周期换向脉冲法快速电沉积可以得到组织致密、内应力小、沉积速率高的 Al2 O3／Ni复合镀层。     

划痕法表征TD处理制备的VC涂层界面结合强度

 为了测定碳化钒(VC)涂层与基体之间的结合强度,分析涂层与基体的结合机制,采用热扩散(TD)处理在冷作模具钢Cr12MoV表面制备了VC涂层,通过扫描电镜(SEM)观察了其表面与界面形貌,利用能谱议(EDS)分析了结合界面的V、C元素的分布,用划痕法测定了涂层与基体的界面结合强度,并对涂层失效机理进行了分析.结果表明,经TD处理制备的VC涂层与基体结合界面为成分梯度界面,二者结合面为成分含量呈梯度变化的过渡层,V元素含量从表面到基体逐渐下降,而C元素含量逐渐上升;其结合界面处化学元素相互结合,形成冶金结合,测得涂层与基体的结合强度平均值为45.7 N;涂层失效形式为界面层的压裂,其结合强度主要与VC涂层残余压应力有关.     

Initial corrosion behavior and mechanism of 7B04 aluminum alloy under acid immersion and salt spray environments

The initial corrosion behavior and mechanism of 7B04 aluminum alloy under acid immersion and salt spray environments（pH = 3.5） are studied by Scanning Electron Microscope（SEM）, optical microscope, Fourier Transform Infrared Spectroscopy（FT-IR）, X-Ray Diffraction（XRD）, potentiodynamic polarization, Electrochemical Impedance Spectroscopy（EIS）, and Scanning Kelvin Probe（SKP）. The results show that pitting corrosion occurs at the initial corrosion stage, and the potential difference between the seco...     

Electrochemical behavior of Ti-6.5Al-2Zr-1Mo-1V alloy under rotating condition with periodically fluctuating current density

Titanium alloy plays a crucial role in the electrochemical field due to its excellent corrosion resistance. The passivation and dissolution behaviors of Ti-6.5Al-2Zr-1Mo-1V（TA15） alloy in Na Cl solution were studied by simulating the electrochemical machining process in a rotating condition, which made the anode in a state with alternating high and low current density. Electron probe micro analysis, ultra-depth microscope, scanning electron microscope, and X-ray photoelectron spectrometer were u...     

Effect of tube-electrode inner diameter on electrochemical discharge machining of nickel-based superalloy

Nickel-based superalloys are widely employed in modern aircraft engines because of their excellent material characteristics, particularly in the fabrication of film cooling holes. How-ever, the high machining requirement of a large number of film cooling holes can be extremely chal-lenging. The hybrid machining technique of tube electrode high-speed electrochemical discharge drilling (TEHECDD) has been considered as a promising method for the production of film cooling holes. Compared with any single machining process, this hybrid technique requires the removal of more complex machining by-products, including debris produced in the electrical discharge machin-ing process and hydroxide and bubbles generated in the electrochemical machining process. These by-products significantly affect the machining efficiency and surface quality of the machined prod-ucts. In this study, tube electrodes in different inner diameters are designed and fabricated, and the effects of inner diameter on the machining efficiency and surface quality of TEHECDD are inves-tigated. The results show that larger inner diameters could effectively improve the flushing condi-tion and facilitate the removal of machining by-products. Therefore, higher material removal efficiency, surface quality, and electrode wear rate could be achieved by increasing the inner diam-eter of the tube electrode.     

铝合金表面稀土耐蚀转化膜

本文评述了铝使合金表面稀土耐蚀转化膜这一技术在国内外的研究进展及研究现状;     

MoSi2 涂层高温抗氧化性能和微观组织

采用真空阴极电弧沉积工艺在铌钨合金喷管内、外表面和铌钨合金试样表面沉积了Mo层,采用真空包渗工艺使Mo层硅化生成MoSi2涂层。利用扫描电子显微镜、能谱、XRD、金相显微镜对Mo层和MoSi2涂层表面和断面微观形貌、结构进行了分析。分析表明:MoSi2涂层的相结构由外向内大致可分为外层(MoSi2)、中间层(NbSi2)和过渡层(Nb5Si3)。高温抗氧化试验结果表明:MoSi2涂层在大气环境下1 800℃的静态抗氧化性能达到了30 h,室温至1 700℃循环热震1 376次。考核热试车情况:发动机在温度1 450℃累计工作了415s,在1 610℃工作了100 s,涂层状况完好。     

Gd、Y 对ZK60 镁合金腐蚀行为的影响

通过盐雾腐蚀实验并结合SEM和XRD分析,研究了稀土元素对锻造态ZK60镁合金腐蚀行为的影响.结果表明,ZK60合金耐蚀性较差,而在ZK60中添Gd、Y后的合金,其耐蚀性明显提高.腐蚀时间相同时,两种合金的微观腐蚀形貌不相同,ZK60合金腐蚀坑的形成时间较早(14 d),而添加Gd、Y后的ZK60合金腐蚀坑的形成时间较晚(21 d),添加Gd、Y后ZK60合金的腐蚀产物相对致密.两种镁合金的腐蚀产物均为Mg(OH)2,Mg(OH)2腐蚀产物膜极易发生开裂,形成网块状的腐蚀产物膜.腐蚀产物膜的进一步生长、开裂和脱落,加速了材料的腐蚀流失.     

内氧化制备A1_2O_3/Cu复合材料载流条件下表面磨损形貌和摩擦学性能研究(英文)

Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.