Structural adhesives with increased deformation resistance

The radiation-resistant cold-setting adhesive compositions with increased elasticity have been developed based on epoxy-diane resin modified by low-molecular two- and three-functional diluents. The presented adhesives can operate in the temperature range of −196 to +150°C, and they yield a high shear strength of the adhesive joint for aluminum alloys (16–23 MPa) and peeling strength for the joint between organic fabrics and aluminum alloys (1.75–2.4 kN/m).     

Customization of the CEFM for predicting stress corrosion cracking in lightly sensitized Al–Mg alloys in marine applications

The Coupled Environment Fracture Model (CEFM) has been modified and calibrated to predict crack growth rate (CGR) in aluminum marine alloys. The customized CEFM provided quantitative predictions of the effects of O₂, electrochemical potential, stress intensity factor, and conductivity on CGR in lightly sensitized AA5083-H321 in 3.5 wt.% NaCl solution, as well as explaining the development of a semi-elliptical surface cracks. The importance of the properties of the external environment, such as conductivity, oxidant/reductant concentration, and the kinetics of the cathodic reactions on the surfaces external to the crack has been confirmed. Crack growth is attributed to a sequence of microfracture events at the crack front, the frequency of which is determined by the mechanical conditions that exist at the crack tip, as governed by the stress intensity while the microfracture dimension is determined by hydrogen-induced fracture, with the CGR being the product of these two quantities. The success in explaining the intergranular stress corrosion cracking (IGSCC) of aluminum alloys, argues that the basic concept of the CEFM, that the internal and external environments are strongly coupled, is sound and that the CEFM, which was originally developed to describe IGSCC in sensitized stainless steels is equally applicable for describing IGSCC in lightly sensitized aluminum alloys.     

铝合金表面改性对有机涂层附着力的影响及腐蚀防护性能研究

利用电化学阻抗（EIS）、扫描微参比技术（SRET）、接触角、粗糙度、附着力、盐雾等测试方法,研究了铝合金阳极氧化与贻贝黏附蛋白（MAP）/CeO₂/硅烷γ-APS（MCA）表面复合修饰的腐蚀防护性能以及对改性聚氨酯涂层附着力和耐蚀性的影响。结果表明,MCA复合膜可抑制铝合金的腐蚀,并具有一定的自修复功能;阳极氧化和MCA表面复合修饰可为铝合金提供有效的早期腐蚀防护作用,且能提高铝合金表面粗糙度和润湿性,显著提升改性聚氨酯涂层在铝合金表面的附着力和耐蚀性,因而结合改性聚氨酯涂层和表面复合修饰可实现对铝合金长期有效的腐蚀防护。     

Effect of Aluminum Alloy Surface Modification on Adhesion of the Modified Polyurethane Coating and Its Corrosion Protective Performance北大核心CSCD

The ordinary organic coatings on aluminum alloy usually encounter a problem of low adhesion to the substrate, which results in destruction and failure of the long-term protective performance of the anticorrosion systems. The surface modification of aluminum alloy is able to enhance the adhesion of organic coating on aluminum alloys, and to improve their protective performance. In this work, a combined surface modification of anodic oxidation and mussel adhesion protein/CeO2/3-aminopropyltriethoxysilane composite film (MCA) was developed on the aluminum alloy. The adhesion of modified polyurethane coated on the treated aluminum alloy and its corrosion protective performance were evaluated comprehensively by using contact angle, adhesion strength, electrochemical impedance spectroscopy (EIS), and scanning reference electrode technique (SRET). The measurements of EIS and SRET demonstrated that the MCA composite film on anodic oxidized Al possessed self-healing function and provided effective protection against early corrosion of aluminum alloy. The pull-off test showed that both anodic oxidation treatment and MCA composite film modification were able to increase the adhesion of modified polyurethane coating on aluminum alloy, and their combined action were supposed to remarkably enhance the adhesion strength up to 17.1 MPa. The reason for the improvement of adhesion was that the anodic oxidation treatment and MCA composite film modification could improve the surface roughness of aluminum alloy, and enhance the surface wettability and surface polarity, which is beneficent to enhance the bonding of the modified polyurethane coating to aluminum alloy surface. The EIS results showed that no any corrosion occurred for the modified polyurethane coating on the treated aluminum alloy during 65 d immersion in 3.5wt.% NaCl solution. The impedance value in low frequency range of the modified polyurethane coating always maintained at a high order of magnitude on the aluminum alloy treated by anodic oxidation and MCA composite film modification, showing an excellent protective performance of the coating system. The evaluation of Neutral Salt Spray (NSS) indicated that the modified polyurethane coating on the treated aluminum alloy owned superior corrosion protection performance, and the adhesion strength remained 13.1 MPa and no any corrosion was found at the scratch locations even after 1200 h of salt spray testing. It was concluded that combination of anodic oxidation and MCA composite film were capable of significantly improving the adhesion of modified polyurethane coating on aluminum alloy and providing long-term effective corrosion protection for aluminum alloy. © 2021 Authors. All rights reserved.     

Electro-ring-spectrophotometry as a nondestructive technique for quantitative analysis of alloys

A combined technique “electro-ring-spectrophotometry” involving electrography, Weisz ring oven, and spectrophotometry has been described, permitting rapid and nondestructive quantitative analysis of three different alloys. Diethylaniline for zinc and a modified aluminon procedure for aluminum, using ring oven has also been described. The results of the analysis are reproducible and accurate.     

The penetration of indium-gallium melt components into aluminum

The penetration of indium-gallium melt into aluminum alloys was studied by X-ray fluorescence spectroscopy, X-ray diffraction, and optical microscopy. The X-ray fluorescence data were used to suggest a method for estimating the bulk diffusion coefficient of liquid gallium into grains of polycrystalline aluminum alloys of various brands.     

Ellipsometric and IR spectroscopic study of the surface interaction of binary Al-REM alloys with water

The effect of Al-REM binary alloys’ composition on the kinetics of their surface oxidation by water is studied by means of ellipsometry and IR spectroscopy. Intermetallides with ～21 at % rare-earth metal in aluminum are oxidized in distilled water at 100°C, along with alloys of eutectic composition (Al-～2 at % REM) in solid and disperse state. It is found that the kinetic dependences of the thickness of films formed on pollycrystalline alloy samples and the IR transmission spectra of dispersed samples show that increasing the quantity of dopant REM in aluminum lowers the reactive capability of aluminum under certain conditions. It is found that the experimental ellipsometric results are described by a two-layer model consisting of a substrate, an inner oxide layer and an outer layer of hydroxide.     

Effect of atmospheric nitrogen on the oxidation mechanism of aluminum alloys with rare-earth metals

Interaction (25–620°C) of aluminum and its alloys with an atmosphere saturated with nitrogen was studied to determine the role played by rare-earth metals in the mechanism by which nitride phases are formed in oxidation of Al + REM alloys in air. The ellipsometric method and Auger electron spectroscopy were used to determine that, under the given experimental conditions, metallic aluminum is subjected to the greatest extent to the nitridation process, which is competing with the oxidation process. The process is initiated by the conversion of the amorphous oxide film to γ-Al₂O₃. The surface of Al + REM alloys interacts with nitrogen at the outer part of the oxide layer. The rare-earth metal actively reacts with impurity oxygen present in the atmosphere under study and hinders formation of nitride/oxynitride layers.     

Correlation between formation conditions and breakdown voltage of anodic oxide films on aluminum

Two series of samples were investigated: a) aluminum films with a sublayer of tantalum; b) industrial aluminum alloys AMg-2m; D16; AMc; AD-1n. The optimum composition of re-anodizing electrolyte was chosen on the basis of a solution of citric acid and ethylene glycol. The results of investigations of the sparking voltage at re-anodizing for various aluminum alloys and thicknesses of primary porous oxide are presented. The analytical dependence of breakdown voltage value on forming voltage value for alloy AD-1n was obtained. The original design of re-anodizing cell allowing increase of the sparking voltage was developed.     

Electrochemical characterisation of laser welding tracks

The advantages of laser welding are high process velocity, the possibility to joint alloys, which are not solderable, and the high bonding strength. During the laser welding process a high energy input in a very short time and a small area is performed, resulting in possible changes of structure and composition. Direct information of the change of the electrochemical behaviour of dental alloys after Laser welding procedure does not exist. The aim of this work was, therefore, to assess the electrochemical behaviour of laser welded joints in comparison with the bulk material using the mini-cell system. The logI vs. E curves performed on the bulk material show a complete change concerning the characteristic data, the shape and the position in comparison to such curves measured on the laser track. The characterisation of the electrochemical behaviour of laser welding tracks seems to be very easy by using the mini-cell system.     

合金中痕量元素标准物质研制进展

通过对国内外高温合金、铝合金痕量元素标准物质的比较,评述了我国合金中痕量元素标准物质在种类、量值水平及不确定度等方面的进展。     

Electroactive conducting polymers for corrosion control

There is an intensive effort underway to develop new corrosion control coatings for structural metals. In part, this effort has been motivated by the desire to replace chromium(VI)-containing coatings currently used for corrosion control of iron and aluminum alloys. Cr(VI) has been shown to be hazardous to the environmental and to human health, and its use in many countries will be sharply curtailed in the coming years. Electroactive conducting polymers (ECPs) represent a class of interesting materials currently being explored for use in corrosion control coating systems, possibly as a replacement for Cr(VI)-based coatings. The electroactivity and the electronic conductivity (or semiconductivity) of ECPs set them apart from traditional organic coatings. As with chromate, interesting and potentially beneficial interactions of ECPs with active metal alloys such as steel and aluminum are anticipated, with concomitant alteration of their corrosion behavior. A review of this active research area will be presented in two parts. Here in Part 1, a general introduction to the topic of corrosion control by ECPs will be presented, including an overview of corrosion and its control by traditional methods, an introduction to ECPs and their properties, and a discussion of the processing issues surrounding the use of ECPs as coatings. Part 1 also includes a review of the literature on the use of ECPs as coatings (or components of coatings) on non-ferrous active metals, principally aluminum and aluminum alloys, although some work on zinc, copper, silver, titanium and silicon will also be described. In Part 2 of this review (to be published in the next issue of this journal), the rather extensive literature on the use of ECPs for the corrosion control of ferrous alloys (steels) will be reviewed. Electronic Publication     

混合稀土对ZL108铝合金组织与性能的影响

对稀土处理前后的ZL108合金进行了机械性能测试和断口分析, 表明稀土处理有利于提高合金的塑性和强度. 对稀土处理前后合金中氢总量进行了分析, 未加稀土的合金内氢总量与稀土处理后的合金相当, 结合性能与断口形态, 从侧面表明稀土改变了氢的存在形式.     

Effect of oxide films on formation of Fe-rich intermetallic phases in aluminum alloys

Journal of Thermal Analysis and Calorimetry - The aim of the present work was to study the effect of the α-Al2O3 and MgAl2O4 oxide films, normally found in cast aluminum alloys, on formation...     

Electrochemical properties and corrosion inhibition of AA6061 in tropical seawater

The corrosion inhibition of aluminum and its alloys is the subject of tremendous technological importance due to the increased industrial applications of these materials. This study reports the results of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) on the corrosion inhibition of AA6061 aluminum alloys in seawater using sodium benzoate as an inhibitor. The electrochemical measurements for aluminum alloys in seawater after varied immersion period showed that the presence of sodium benzoate significantly decreases the corrosion currents densities (i_corr), corrosion rates and double layer capacitance (C_dl), as simultaneously increase the values of polarization resistance (R_p). Charge transfer process and development of thin film on the specimen have been proven by morphology study using SEM.     

Phase transformations in rapidly quenched Al–Cr–Zr alloys during heat treatment

Results from studying the effect zirconium has on solid-phase processes in aluminum–chromium alloys are presented. Rapidly quenched alloys are prepared via melt spinning. The quenching rate is ~10⁶ K/s. By means of physicochemical analysis, it is shown that doping Al–Cr alloys with zirconium improves the thermal stability of supersaturated solid solutions and stabilizes their microcrystalline structure; this hinders the coagulation of intermetallic phases and thus improves the hardness of the alloys. It is found that supersaturated solid solutions of Cr and Zr in aluminum undergo stepwise decomposition; the temperature and time parameters of each step are shown in TTT diagrams.     

Mechanical properties of UV‐curable carbon fiber‐reinforced polymer composite patch: Repair evaluation of damaged aluminum alloy

Epoxy resin composite patches reinforced by carbon fiber were prepared through ultraviolet (UV)–curing method, and the damaged aluminum alloy plates are rapidly repaired by means of adhesively bonding method. Mechanical properties of the composite patches and damaged aluminum alloy plates before and after repair were studied by experiment and numerical simulation. Results indicated that the tensile properties of carbon fiber/epoxy resin composite patches presented the tendency of first increase and then decrease with the increase of layer numbers of reinforced fiber. The composite patches with two layers fiber showed the best tensile properties, and the tensile strength and modulus reached 1.13 GPa and 27.79 GPa, respectively. However, the bending strength of composite patches decreased with the increase of layer numbers. Results of performance evaluation on the mechanical properties of damaged aluminum alloy plates repaired by the two layers carbon fiber/epoxy resin composite patches showed that the repair efficiency of tensile and bending properties of the repaired aluminum alloys reached more than 83% and 160%, respectively, compared with the undamaged aluminum alloys. Besides, results of numerical simulation showed that the stress intensity factor (SIF) of the crack tip on repaired aluminum alloy plates decreased significantly in comparison with the unrepaired aluminum alloy plates, which further revealing the reinforced mechanism of composite patches on the bending properties of repaired aluminum alloy plates.     

Formation and dielectric properties of anodic oxide films on Zr–Al alloys

Zr–Al alloys containing up to 26 at.% aluminum, prepared by magnetron sputtering, have been anodized in 0.1 mol dm⁻³ ammonium pentaborate electrolyte, and the structure and dielectric properties of the resultant anodic oxide films have been examined by grazing incidence X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, and AC impedance spectroscopy. The anodic oxide film formed on zirconium consists of monoclinic and tetragonal ZrO₂ with the former being a major phase. Two-layered anodic oxide films, comprising an outer thin amorphous layer and an inner main layer of crystalline tetragonal ZrO₂ phase, are formed on the Zr–Al alloys containing 5 to 16 at.% aluminum. Further increase in the aluminum content to 26 at.% results in the formation of amorphous oxide layer throughout the thickness. The anodic oxide films become thin with increasing aluminum content, while the relative permittivity of anodic oxide shows a maximum at the aluminum content of 11 at.%. Due to major contribution of permittivity enhancement, the maximum capacitance of the anodic oxide films is obtained on the Zr–11 at.% Al alloy, being 1.7 times than on zirconium at the formation voltage of 100 V.     

Formation and properties of composite coatings on aluminum alloys

A study was made into the morphology, composition, and electrochemical and mechanical properties of protective composite coatings on various aluminum alloys, including those doped with Sc, Cu, and Ni. It was established that protective coatings significantly increase the corrosion resistance of the alloys in a 3% NaCl solution. Composite coatings produced by triple dip coating in an superdispersed polytetrafluoroethylene suspension have unique corrosion-resistance properties, reducing the corrosion current density for all the protected alloys to 3.1 × 10^–11–4.0 × 10^–12 A/cm², which is more than three orders of magnitude lower than that for coatings formed by plasma electrolytic oxidation and five orders of magnitude lower than that for alloys without coating.     

快速凝固Ni-Zr-Al非晶态催化合金的制备与活化处理

As new catalytic materials, amorphous alloys have attracted much attention since 1980s. Rapid solidification is one of the main techniques to prepare amorphous alloys.However, as-cast rapidly solidified alloys usually can not be directly used as the catalyst for their poor surface area, oxide film on their surface, etc. Therefore, activation pretreatment must be carried out. Recently, leaching aluminum has been attempted to activate rapidly solidified amorphous catalytic alloys containing aluminum. In order to carry out such an activation pretreatment, the Al-rich amorphous precursor alloys must be obtained first, in which the content of active component must be sufficiently high so that the catalytic activity of the activated catalyst can be attained. On the other hand, the chemical composition of the precursor must approach eutectic point or contribute to the range of low liquidus temperature so that the glass transition can be easily achieved according to the solidification theory[1]. So far Al-based alloys which meet the dual confinement have not been found yet. For Ni-Al and Cu-Al systems,only the microcrystalline alloys can be obtained through rapid solidification[2,3].In the present study, glass formation was achieved by introducing promotion elements in Ni-Al system precursor alloys.