汽车用2024铝合金阳极氧化膜性能的研究

对汽车用2024铝合金板材进行酒石酸阳极氧化处理,并研究了阳极氧化对铝合金的成分、结构、表面形貌及耐蚀性的影响。研究发现,铝合金阳极氧化膜是由表面多孔层和内部无孔层构成的。铝合金阳极氧化过程是一个氧化铝生成和溶解的动态过程。阳极氧化膜由刚玉结构的α-Al_2O_3和八面结构的γ-Al_2O_3构成,α相和γ相大大提高了阳极氧化膜的硬度和耐蚀性。阳极氧化膜为典型的多孔结构,孔洞分布均匀,孔径为50nm左右。     

铝合金阳极氧化膜性能的研究

研究了2 024铝合金在硫酸溶液中经不同氧化电压阳极氧化处理后的表面形貌、组织结构、硬度和耐蚀性。结果表明:铝合金经不同氧化电压阳极氧化处理后,其表面上存在纳米级的孔洞;随着氧化电压的增大,孔径逐渐增大,膜厚增加;阳极氧化膜的硬度在氧化电压为20V时最大;氧化电压对阳极氧化膜耐蚀性的影响很大,在氧化电压为5V时,阳极氧化膜的耐蚀性最强,自腐蚀电位为-1.1V。     

铝合金阳极氧化膜的性能研究

在硫酸电解液中加入适量由羧酸和有机化合物组成的添加剂,制得铝合金阳极氧化膜。研究了温度对所得氧化膜厚度和硬度和影响,并利用扫描电镜观察了氧化膜的结构。结果表明,高温下形成的氧化膜结构松散,厚度和硬度低,而加入添加剂后,氧化膜溶解减慢,在高温下所形成的氧化膜的厚度和硬度大大增加。     

6063铝合金多种阳极氧化封孔膜性能比较

本文针对6063铝合金阳极氧化膜分别进行沸水封孔、高浓度K2Cr2O7封孔、低浓度K2Cr2O7封孔、Ni2+封孔、Ni2+-Co2+封孔、CeCl3封孔。采用场发射扫描电子显微镜(FESEM)观察封孔膜的表面形貌,测试封孔膜的磷-铬酸失重并采用动电位法测氧化膜在NaCl腐蚀介质中Tafel腐蚀极化曲线,结果表明CeCl3封孔膜失重最小,具有良好的耐蚀性,对铝基体具有较好的保护作用。     

硫酸阳极氧化对7A65航空铝合金疲劳性能的影响

[目的]铝合金零件的疲劳性能是决定飞机服役寿命的关键因素。硫酸阳极氧化是铝合金零件常用的表面处理工艺,研究其对铝合金疲劳性能的影响对指导生产极其重要。[方法]针对新型航空铝合金7A65,采用重复退膜-阳极氧化的方式开展实验。通过疲劳试验机对试样进行疲劳性能测试,绘制应力-疲劳寿命曲线,分析和对比重复退膜和阳极氧化不同次数后7A65铝合金的疲劳性能。通过体视显微镜和扫描电子显微镜对典型断口形貌进行分析,并探讨了其疲劳失效机制。[结果]7A65铝合金在重复退膜-阳极氧化处理后疲劳极限明显下降。经过2次阳极氧化,7A65铝合金的疲劳极限下降为原疲劳极限的61.1%;继续进行退膜-阳极氧化处理,疲劳极限下降趋缓,4次阳极氧化后的疲劳极限为原疲劳极限的56.5%。在此过程中,其疲劳断口呈现出由单一裂纹源向多裂纹源,以及从韧性断裂向脆性断裂的转变。[结论]硫酸阳极氧化对7A65铝合金疲劳性能的影响较大,在生产中应当控制阳极氧化零件的返修次数。     

硫酸铈对铝合金阳极氧化膜耐蚀性的影响

通过正交试验确定铝合金硼酸和硫酸电解液阳极氧化的最佳电压、时间和温度,分别在基础配方溶液中添加不同含量的硫酸铈,对所制的样品氧化膜进行盐雾和浸泡耐蚀性测试,采用测量极化曲线的方法求出了φcorr和Jcorr,确定硫酸铈的最佳添加量.     

铝合金的阳极氧化及其研发进展

铝合金阳极氧化技术能够提高基体表面的耐蚀性、耐磨性及硬度等,不同酸性工艺条件下能够得到不同性能的阳极氧化膜。文章概述了常规酸性电解液下的阳极氧化,着重介绍了硼酸和硫酸阳极氧化的工艺及发展,简明指出了阳极氧化的发展趋势。     

电流密度对铝合金瓷质阳极氧化膜性能的影响

在草酸钛钾电解液中采用恒流模式对铝合金进行瓷质阳极氧化处理,研究了电流密度对瓷质阳极氧化膜的耐蚀性、厚度以及硬度的影响。结果表明:随着电流密度的增加,瓷质阳极氧化膜的耐蚀性、厚度以及硬度都有所提高;当电流密度为2.5A/dm2时,瓷质阳极氧化膜的耐蚀性最佳,厚度最大。     

不同阳极氧化工艺对铝合金支架表面氧化膜性能的影响

本文分别采用硫酸、草酸以及酒石酸阳极氧化工艺对铝合金支架进行阳极氧化处理,比较了采用不同工艺阳极氧化处理后支架的外观,表征了不同氧化膜的相结构,并测试了不同氧化膜的耐腐蚀性能、硬度和耐磨性能.结果表明,采用不同工艺阳极氧化处理后支架的外观与裸支架基本相同,都具有银白色光泽.不同氧化膜的物相都以Al相为主,还有α-Al2O3相和γ-Al2O3相,且都能提高铝合金基体的耐腐蚀性能、硬度和耐磨性能.与硫酸氧化膜相比,草酸氧化膜和酒石酸氧化膜的性能相对较好,主要归因于草酸和酒石酸对氧化膜的溶解性较弱,制备的氧化膜致密程度较高.酒石酸氧化膜具有良好的致密度,其硬度最高,达到357 HV,耐腐蚀性能和耐磨性能都最好,因此酒石酸阳极氧化工艺更适用于铝合金支架阳极氧化处理,能较大幅度提高铝合金支架的性能.     

铸铝合金硫酸阳极氧化

研究了铸铝合金的表面预处理和阳极氧化工艺;讨论了铸铝合金的表面预处理和工艺条件对阳极氧化膜耐蚀性与厚度的影响;获得了合适的表面预处理方法和阳极氧化工艺条件。     

Effect of aluminum annealing on the galvanoluminescence properties of anodic oxide films formed in organic electrolytes

The galvanoluminescence (GL) properties of anodic oxide films formed in organic electrolytes were investigated at different aluminum annealing temperatures. The results of the spectral measurements showed two different types of GL sources: carboxylate ions incorporated in oxide films during the anodization and the molecules AlH, AlO, Al₂, AlH₂, also formed during anodization process and already recognized in the case of inorganic electrolytes. The latter was related to gamma alumina crystalline regions formed by annealing of the aluminum samples at temperatures above 500 °C.     

Sealing effects of anodic oxide films formed on Mg-Al alloys

Mg alloys were anodized in alkaline NaOH solutions with various additives as a non-chromate method. Specimen AZ91 was anodized at a potential that produced a strong surface dissolution reaction and generated a large amount of Mg(OH)₂. The effect of sealing after anodizing was investigated, focusing on the effects of sealing time, temperature and solution conditions. The current density decreased with increasing A1(OH)₃ concentration in 1 M NaOH solution during anodizing; sparking occurred at potentials above 80 V. The best corrosion resistance with anodizing in 1 M NaOH solution occurred at a potential of 4 V, which caused the strongest active dissolution reaction. The sealing effect improved with increasing time and temperature, and corrosion resistance was proportional to the relative ratio of Mg(OH)₂. If the oxygen thickness observed by EDX equaled the film thickness, the film formed at 4 V in 1 M NaOH was 10–15 Μm thickness. The optimum corrosion resistance in sealing at various solutions after anodizing was 1M-NaOH solution.     

Luminescence properties of oxide films formed by anodization of aluminum in 12-tungstophosphoric acid

In this paper, we have investigated luminescence properties of oxide films formed by anodization of aluminum in 12-tungstophosphoric acid. For the first time we have measured weak luminescence during anodization of aluminum in this electrolyte (so-called galvanoluminescence GL) and showed that there are wide GL bands in the visible region of the spectrum and observed two dominant spectral peaks. The first one is at about 425 nm, and the second one shifts with anodization voltage. As the anodization voltage approaches the breakdown voltage, a large number of sparks appear superimposed on the anodic GL. Several intensive band peaks were observed under breakdown caused by electron transitions in W, P, Al, O, H atoms. Furthermore, photoluminescence (PL) of anodic oxide films and anodic-spark formed oxide coatings were performed. In both cases wide PL bands in the range from 320 nm to 600 nm were observed.     

The galvanoluminescence spectra of barrier oxide films on aluminum formed in organic electrolytes

In this paper, for the first time we have presented the results of the galvanoluminescence (GL) spectra measurement obtained from barrier oxide films during aluminum anodization in various barrier film forming organic electrolytes (aqueous solution of citric acid, tartaric acid, malic acid, succinic acid and ammonium tartarate). Galvanoluminescence spectral measurements were performed utilizing spectrograph system based on the Intensified Charge Coupled Device (ICCD) camera, intended for time-resolved detection of GL phenomena dynamics. The spectra were recorded for different values of electrolyte temperature and anodization current density. We have showed that there are strong GL bands in the visible region and the shape of the spectra as well as peak intensity of the GL bands depend on the anodization voltage. The results cleraly indicate the existance of more then one type of GL centra or GL mechanisms in barrier films formed in organic electrolytes.     

Anodically formed oxide films on niobium: Microstructural and electrical properties

The electrical and structural properties of nanoscale niobium pentoxide (Nb₂O₅) dielectric layers in niobium-based solid electrolyte capacitors were studied. The Nb₂O₅ layers are formed by anodic oxidation of Nb-powder compacts. Capacitance measurements show a strong bias-voltage dependence of the capacitance after anodization. Heat treatments at temperatures up to 320 °C, which are applied in the capacitor-production process, lead to an increase of the capacitance and a reduction of the bias dependence. Based on the electrical and structural properties, which are characterized by electron microscopic techniques, a model is presented which explains the behavior of the specific capacitance after the various processing steps.     

Electronic properties of thermally formed thin iron oxide films

The oxide layer, present between an organic coating and the substrate, guarantees adhesion of the coating and plays a determinating role in the delamination rate of the organic coating. The purpose of this study is to compare the resistive and semiconducting properties of thermal oxides formed on steel in two different atmospheres at 250 °C: an oxygen rich atmosphere, air, and an oxygen deficient atmosphere, N₂. In N₂, a magnetite layer grows while in air a duplex oxide film forms composed by an inner magnetite layer and a thin outer hematite scale. The heat treatment for different amounts of time at high temperature was used as method to sample the thickness variation and change in electronic and semiconducting properties of the thermal oxide layers. Firstly, linear voltammetric measurements were performed to have a first insight in the electrochemical behavior of the thermal oxides in a borate buffer solution. Electrochemical impedance spectroscopy in the same buffer combined with the Mott-Schottky analysis were used to determine the semiconducting properties of the thermal oxides. By spectroscopic ellipsometry (SE) and atomic force microscopy (AFM), respectively, the thickness and roughness of the oxide layers were determined supporting the physical interpretation of the voltammetric and EIS data. These measurements clearly showed that oxide layers with different constitution, oxide resistance, flatband potential and doping concentration can be grown by changing the atmosphere.     

NaF添加剂对铝合金等离子电解氧化陶瓷膜形成的影响

研究了Na2SiO3-KOH电解溶液中添加NaF对铝合金等离子电解氧化陶瓷膜形成的影响。研究表明：电解溶液中加入NaF可加速氧化物陶瓷膜的形成，提高其硬度。NaF的最佳加入量为0．5～0．75g／L。     

Dynamic fatigue of ceramics based on aluminum oxide

A comparative study of the resistance of alumina-based ceramic materials with different grain-boundary phases to delayed fracture is described. The tests were conducted by the method of dynamic fatigue in air, water, and a salt solution. It is shown that the ceramics with an alkali-free vitreous phase has a higher resistance to subcritical crack growth than the material with an alkali-containing grain-boundary phase.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 11, pp. 2 – 4, November, 1996.     

超声波对铝阳极氧化工艺及膜层性能的影响

将超声波应用于铝的阳极氧化处理,研究了超声波对阳极氧化特性曲线、电解工艺参数和膜层形貌的影响。结果表明,超声波能增加氧化膜的生长速率,提高阳极氧化温度与氧化电流密度的上限值,可实现在较高温度和大电流密度下对铝进行阳极氧化。超声波作用下获得的铝氧化膜层表面孔隙率低,膜层均匀,膜的厚度与硬度都比不加超声波体系有明显提高。     

Photoelectrochemical study of nickel base alloys oxide films formed at high temperature and high pressure water

The oxide film formed on nickel base alloys at high temperature and high pressure water exhibits semi-conducting properties evidenced by photocurrent generation when exposed to monochromatic light. The use of macro- and micro-photoelectrochemical techniques (PEC and MPEC) aims to identify the different semiconductor phases and their distribution in the oxide film.Three different nickel base alloys were corroded in recirculation loop at 325 °C in pressurised water reactor primary coolant conditions for different exposition durations.PEC experiments on these materials enable to obtain macroscopic energy spectra showing three contributions. The first one, with a band gap around 2.2 eV, was attributed to the presence of nickel hydroxide and/or nickel ferrite. The second one, with a band gap around 3.5 eV, was attributed to Cr₂O₃. The last contribution, with a band gap in the range of 4.1-4.5 eV, was attributed to the spinel phase Ni_1−xFe_xCr₂O₄. In addition, macroscopic potential spectra recorded at different energies highlight n-type semi-conduction behaviours for both oxides, Cr₂O₃ and Ni_1−xFe_xCr₂O₄.Moreover, MPEC images recorded at different energies exhibit contrasted regions in photocurrent, describing the distribution of nickel hydroxide and/or nickel ferrite and Cr₂O₃ in the oxide film at a micron scale.It is concluded that PEC techniques represent a sensitive and powerful way to locally analyse the various semiconductor phases in the oxide scale.