Anodising of Al 2024-T3 in a modified sulphuric acid/boric acid bath for aeronautical applications

A novel borate/boric/sulphuric acid anodising process is studied. The results show that the physical structure of the films is influenced not only by the bath used, but also and mainly by the substrate, i.e., Al 2024-T3 or Al. The corrosion resistance of the anodised specimens is satisfactory for practical applications and the fatigue resistance is not significantly different from that obtained with the traditional chromic acid anodising.     

2024-T3铝合金在硫酸-硼酸-磷酸中的阳极氧化和腐蚀行为

在含有10%硫酸、5%硼酸和2%磷酸的混合电解液中,对2024-T3铝合金进行阳极氧化处理,以提高其耐腐蚀性能。使用电化学阻抗频谱分析研究阳极氧化处理后合金的腐蚀行为。利用塔菲尔图和盐水喷雾技术进行对比发现,与只用磷酸或硫酸和硼酸的电解液相比,使用含有10%硫酸、5%硼酸和2%磷酸的混合电解液阳极氧化处理后的2024-T3铝合金,具有更好的耐腐蚀性和持久性。该电解液可以替代普遍用于阳极氧化铝合金的铬酸盐浴。     

铝质材料上电镀镍及预处理工艺的研究

采用浸镀Ｚｎ－Ｎｉ合金预处理工艺,在铝质材料表面可制得结合力良好,外观平整光滑的镀镍层,与磷酸阳极氧化处理和二次浸锌处理相比,结晶更细致,镀层质量更好。添加剂能明显改善镀层质量。镀镍对铝质材料的表面改性效果明显。     

Formation of subsurface crevices in aluminum alloy 2024-T3 during deposition of cerium-based conversion coatings

The processing variables that contributed to the formation of subsurface crevices under cerium-based conversion coatings on AA 2024-T3 were investigated. Focused ion beam milling revealed the presence of subsurface crevices underneath a small fraction (∼ 10%) of coated areas, typically in areas with large cracks through the coatings. A solution of sodium chloride and H₂O₂ etched AA 2024-T3 and produced features similar to subsurface crevices, which confirmed that crevices formed during deposition due to the composition of the coating solution. Using sodium nitrate in place of sodium chloride resulted in no etching of the substrate. Thus, coatings free of subsurface crevices could be produced by using cerium nitrate instead of cerium chloride in the coating solution. Electrodeposited coatings, even those deposited from solutions containing chloride ions and H₂O₂, were also free of subsurface crevices. As a result, subsurface crevices are not inherent to cerium-based conversion coatings, but rather were formed due to certain process parameters, specifically the presence of chloride ions and hydrogen peroxide in the coating solution.     

2014、2024铝合金挤压棒材的组织与性能研究

对2014、2024铝合金挤压棒材分别进行淬火、时效等工艺处理后,采用电子万能试验机及金相显微镜分析比较了2014、2024铝合金挤压棒材的组织和性能。结果表明:2014合金相对于2024合金具有更好的高温强度,当测试温度达到200℃时,合金强度才会明显的降低。     

高强铝合金裂纹尖端在3.5%NaCl溶液中的微区电化学特性

采用毛细管微电极测试方法、扫描Kelvin探针技术和数值分析方法,对2024 T351高强铝合金裂纹尖端在3.5%NaCl溶液中的微区电化学特性和腐蚀行为进行了研究.结果表明,裂纹尖端的腐蚀电位较远离裂纹尖端的基体位置更负,裂纹尖端处的电化学活性明显增加.在外加应力的作用下,裂纹尖端处表面氧化膜的厚度减薄,其稳定性和保护性变弱.裂纹尖端处优先发生阳极溶解,浸泡24 h后在裂纹尖端处出现腐蚀产物的堆积.由于腐蚀电位和电化学活性的差异,在裂纹尖端(阳极)和远离裂纹尖端的基体(阴极)之间可形成电偶对,进一步促进裂纹尖端局部区域内腐蚀过程的进行.     

Novel hybrid organo-silicate corrosion resistant coatings based on hyperbranched polymers

Corrosion protective sol-gel coatings were developed on AA2024-T3 through an aqueous sol-gel process (Modified Self-Assembled Nanophase Particle method) which includes in-situ formation of a dense silica network from hydrolyzed 3-glycidoxy-propyltri-methoxysilane and tetraethoxysilane by proper cross-linking. In the present study, hyperbranched poly(ethylene imine) of two different molecular weights was investigated as a cross-linking agent since this polymer is able to solubilize non-water-soluble organic molecules. In this respect, two organic corrosion inhibitors (2-mercaptobenzothiazole and 2-mercaptobenzimidazole) were combined with poly(ethylene imine) to induce self healing properties. The as developed coatings were also compared with Si/Zr containing coatings developed by a solvent based sol-gel technique. The potentiodynamic scan and the electrochemical impedance spectroscopy methods were employed to evaluate the corrosion protection performance, whereas the chemical structure, morphology and integrity of the coatings were evaluated by Fourier transformed infrared spectroscopy and scanning electron microscopy studies. Formulations that contain poly(ethylene imine) demonstrate better corrosion barrier properties compared to formulations cross-linked with the simple molecule of diethylenetriamine in all cases and especially when combined with the organic inhibitors.     

高强铝合金裂纹尖端在3.5%NaCl溶液中的微区电化学特性

采用毛细管微电极测试方法、扫描Kelvin探针技术和数值分析方法,对2024-T351高强铝合金裂纹尖端在3.5%NaCl溶液中的微区电化学特性和腐蚀行为进行了研究.结果表明,裂纹尖端的腐蚀电位较远离裂纹尖端的基体位置更负,裂纹尖端处的电化学活性明显增加.在外加应力的作用下,裂纹尖端处表面氧化膜的厚度减薄,其稳定性和保护性变弱.裂纹尖端处优先发生阳极溶解,浸泡24 h后在裂纹尖端处出现腐蚀产物的堆积.由于腐蚀电位和电化学活性的差异,在裂纹尖端(阳极)和远离裂纹尖端的基体(阴极)之间可形成电偶对,进一步促进裂纹尖端局部区域内腐蚀过程的进行.     

常压空气等离子处理对铝合金胶接接头强度的影响

为改善铝合金表面润湿性与胶接强度,采用常压空气射流等离子体对5052铝合金进行表面处理。通过接触角测试,表面自由能计算和胶接接头剪切强度测试表明处理时间对铝合金表面改性效果影响不大,随着处理距离减短,铝合金表面自由能、胶接接头强度均逐步提升。处理距离为5 mm时等离子处理铝合金获得最佳表面改性效果,铝合金胶接接头剪切强度由10.6 MPa提升至19.3 MPa,失效模式由界面失效转变为内聚失效。利用SEM,XPS,傅立叶变换红外光谱等检测手段分析不同处理距离对应表面理化特性的变化,结果表明:处理距离较远时,等离子体并未改变铝合金表面物理形貌,其主要改性效果体现为表面清洗;处理距离较近时,铝合金表面高温熔融产生复杂微结构的粗糙氧化层,同时氧化层表面吸附羟基等极性官能团,显著提升了其表面自由能与胶接强度。     

铝合金的激光表面热处理现状

综述了通过激光合金化、激光涂覆、激光熔凝,激光冲击,激光表面强化等表面热处理,改善铝合金表面硬度,耐磨性,抗疲劳等力学性能的研究现状及应用效果。     

Synergistic effect of pH and oxalate concentration on corrosion of aluminium alloy 2024-T3

This work aims at obtaining comprehensive information on the corrosion behaviour of AA2024-T3 in oxalic acid solutions under different concentrations (0.007–0.2?M) and pH (2–6). Various tests to characterise the corrosion behaviour are performed, including weight loss and electrochemical tests. Coupon surfaces are examined using infinite-focus microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Raman spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy. Corrosion rates, anodic and cathodic reaction kinetics are detailed to provide a fundamental understanding of the electrochemical behaviour of AA2024-T3 as a function of pH and oxalate concentration. The synergistic effect of pH and oxalate concentration on corrosion of AA2024-T3 is evaluated for both AA2024-T3 matrix and main intermetallics (i.e. Al–Cu–Mg and Al–Cu–Fe–Mn) and the electrochemical behaviour of each constituent element in AA2024-T3 is systematically studied.     

激光除漆对铝合金飞机蒙皮微观组织的影响

目的 探究激光除漆对铝合金飞机蒙皮基体近表层(15 μm)微观组织的影响规律,阐明近表层微观组织变化与显微硬度的内在联系。方法 采用纳秒脉冲红外激光去除2024-T3铝合金飞机蒙皮表面漆层,通过调节激光能量密度,分别除漆至基体阳极氧化层、铝合金、铝合金表面熔融。利用激光扫描共聚焦显微镜(LSCM)表征漆层的剥离程度及基体的表面形貌。通过超景深三维显微镜(OM)、扫描电子显微镜(SEM)、Image-Pro Plus软件表征Keller试剂腐蚀后铝合金基体近表层的微观组织。采用数显显微维氏硬度计测量基体剖面的显微硬度。结果 在激光能量密度为4.26 J/cm²时,相较于原始基体,阳极氧化层较完整,其基体的表面粗糙度接近于原始基体(未除漆),近表层的微观组织无明显改变,近表层的显微硬度增加了1.6%。当除漆至铝合金基体表面完整时(15.25 J/cm²),相对于原始基体,其表面粗糙度降低,近表层的微观组织无明显改变,近表层的显微硬度增加了4.8%。在激光能量密度为27.79 J/cm²时,铝合金表面熔融,其表面粗糙度相对于原始基体增大,近表层的晶粒显著细化,其显微硬度增加了17.3%。结论 采用合适的激光能量密度对铝合金飞机蒙皮进行激光除漆,不会显著改变其基体近表层的微观组织。在较高能量密度下,铝合金近表层会发生晶粒细化,导致显微硬度显著增加。     

铝合金搅拌摩擦焊物理场三维数值模拟

基于热物理模拟构建的2024-T3铝合金Arrhenius本构关系,使用Deform-3D软件建立了搅拌摩擦焊三维热-力耦合模型,模拟焊接过程温度、应力、应变等物理场在塑性变形区的分布状态. 结果表明,各物理场受焊速和转速的影响均呈不对称分布,其中材料在前进侧表现为压应力状态,在后退侧出现受拉应力状态;此外,在前进侧材料分别向焊缝表面和根部流动,当材料由后退侧向前进侧的流动速度小于在厚度方向上的流动速度时,在焊缝内产生缺陷,并通过试验验证了这一现象.     

铝合金表面激光熔覆研究现状

总结了铝合金表面激光熔覆的特点,评述了铝合金表面激光熔覆技术的处理工艺和熔覆体系的研究现状,分析了各种熔覆层的组织特征及性能,阐明了铝合金激光表面熔覆存在的主要问题和改进途径,并提出了今后的任务.     

含双氧水磨液对铝合金滚磨光整加工的影响

目的探索含双氧水磨液对铝合金试件滚磨光整加工后表面质量的影响及作用机理。方法在相同条件下,配制含不同浓度双氧水的磨液作为液体介质,对铝合金试件进行滚磨光整加工实验及摩擦磨损实验,测量铝合金试件滚磨光整加工前后的表面粗糙度值,并表征铝合金试件滚磨光整加工前后的表面形貌以及摩擦磨损实验后的磨痕形貌。分析摩擦磨损实验后,铝合金试件表面元素的变化情况,以及滚磨光整加工后,铝合金试件硬度随表面深度的变化情况。结果含双氧水磨液作用下的试件的表面粗糙度值下降率大于去离子水条件下的值,且其摩擦系数和磨损量明显小于去离子水及干式摩擦磨损作用下的值。试件表面初始粗糙度值较小时,含双氧水磨液对滚磨光整加工铝合金试件的作用明显,其中双氧水体积分数为0.3%的磨液作用下Ra从未加工时的0.220μm减小到0.055μm,表面粗糙度值下降率为74%。结论含双氧水的磨液对较低初始表面粗糙度值的铝合金试件经滚磨光整加工后的表面质量具有重要作用。由于磨液对铝合金的吸附、润湿作用,使得其在滚磨光整加工中具有一定的润滑性、清洗性,并且摩擦作用下会使铝合金表面发生一定的摩擦化学反应。磨液中的双氧水加快了铝合金表面的腐蚀氧化反应,并将氧化产物以颗粒的形式拔出表面。滚磨光整加工作用硬化了铝合金表面,提高了其机械性能。     

An electrochemical and superficial assessment of the corrosion behavior of AA 2024-T3 treated with metacryloxypropylmethoxysilane and cerium nitrate

The present work aims at studying the corrosion behavior of treatments based on the deposition of layers of metacryloxypropylmethoxysilane (MAOS) and/or cerium nitrate on aluminum alloy 2024 T-3 (AA2024-T3). The corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) during immersion in 0.1 M Na₂SO₄ and NaCl solutions. Atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were also used to perform a surface analysis before and after the treatments. The electrochemical results show that cerium nitrate, when present between two layers of MAOS (sandwich-type deposited layer), improves the corrosion resistance. This can be attributed to the presence of an internal layer rich in silicium and cerium and another external MAOS layer, which further improves the barrier effect of the layer.     

中国铝型材挤压工业回眸与展望

中国的铝材挤压工业始于１９５６年的东北轻合金加工厂建成投产,当时有从苏联引进的水压机１１台,形成管、棒、型、线生产能力６ｋｔ／ａ。在６０及７０年代又建成了西北铝加工厂、西南铝加工厂的挤压车间及分布在全国各地的６个挤压厂,它们的挤压铝材总生产能力为２３．２ｋｔ／ａ。１９７０年,中国从日本宇部兴产公司引进８台铝型材油压挤压机。改革开放以来,是中国铝型材挤压工业大发展时期特别是８０年代中期及９０年代中期     

常用铝合金及其热处理工艺

对国内外常用铝合金及其牌号对照等相关信息进行了总结,列出了国内外常用铝合金的牌号对照表,并根据铝合金在汽车工业中的应用状况,简述了铸造铝合金A356和锻造铝合金6082的热处理和表面处理,推荐了可行的热处理工艺。     

The impact fracture behavior of aluminum alloy 2024-T351: Influence of notch severity

In this paper, the interactive influences of notch severity and test temperature on the impact properties and fracture behavior of a Al-Cu-Mg alloy 2024 in the T351 microstructural condition is presented and discussed. Notch angles of 45, 60, 75, and 90° were chosen for a standard Charpy impact test specimen containing two notches. For a given angle of the notch, an increase in dynamic fracture toughness, with test temperature, is most significant for the least severe of the notches, i.e., 45°. At a given test temperature, the impact toughness decreased with an increase in notch severity. An increase in notch severity resulted in Mode I dominated failure at all test temperatures. The influence of localized mixed-mode loading is minimal for the alloy in the T351 microstructural condition. The impact fracture behavior of the alloy is rationalized in light of alloy microstructure, mechanisms governing fracture, and the deformation field ahead of the propagating crack.     

Bonding strength in structural adhesive bonded joint

Adhesive bonding has emerged as a unique and highly developed joining process with applicability to a wide variety of engineering materials. Because the stresses of adhesive bonded joints are distributed much more uniformly than mechanical fasteners and many welds, they can be used to improve fatigue resistance and to join thin or fragile parts. This study is to investigate whether welding structure can be replaced by adhesive bonding as structural joints. The bonding strength was evaluated with the manufacturing factors of overlap length, overlap width, added pressure and surface treatment. These data provide bonding structure with design criterion and contribute to raising productivity and reducing in cost.