稀土铝合金化对穿孔顶头组织性能及氧化膜的影响

采用金相、扫描电镜和X射线衍射等分析手段,研究稀土铝合金化对穿孔顶头组织性能及氧化膜的影响。研究结果表明,稀土铝合金化可提高材料的硬度、强度及氧化膜的致密度。     

阳极氧化和硅烷化增强LY12铝合金耐腐蚀性能

采用阳极氧化法在LY12铝合金表面获得了多孔阳极氧化膜,再采用溶胶-凝胶法在其表面制备了γ-环氧丙氧丙基三甲氧基硅烷(GPTMS)/正硅酸乙酯(TEOS)杂化膜。极化曲线与电化学阻抗谱(EIS)研究表明,铝合金阳极氧化膜的维钝电流密度随浸泡时间延长而逐渐增大,但至试验结束其维钝电流密度仍低于裸铝合金约2个数量级。铝合金阳极氧化膜经硅烷杂化溶胶封闭后,其耐蚀性得到显著提高,浸泡822h后,阳极维钝电流密度仍能保持在10~(-5)A/cm~2,低频阻抗值仍达到10~6Ω数量级。扫描电镜(SEM)观察表明,铝合金阳极氧化膜为多孔结构,利于增强硅烷杂化膜与金属基体间的结合性能,显著提高阳极氧化铝合金电极的耐蚀性能。     

激光热处理对7475铝合金阳极氧化膜表面-界面性能的影响

利用阳极氧化法在7475铝合金表面制备一层氧化膜,通过激光热处理(LHT)对氧化膜进行改性处理,采用扫描电子显微镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)分析氧化膜表面-界面形貌、化学元素分布和物相,并对其表面和结合界面化学元素进行面扫描和线扫描分析,研究激光热处理对氧化膜组织和性能的影响。结果表明:激光热处理后,7475铝合金氧化膜表面孔洞增多,界面形成致密热影响区;氧化膜主要由Al_2O_3和SiO_2组成,而热影响区主要由Al_2O_3组成;Al、O、Si原子在结合界面发生富集现象,其界面为化合物型+扩散型形式。     

小电流镀铜对LC4铝合金阳极氧化膜的改性作用

将LC4铝合金进行硫酸阳极化处理,然后采用小电流密度（0.1 mA/cm^2）进行镀铜处理。XRD和EDS分析表明,小电流镀铜的沉积产物为金属铜,沉积的位置位于氧化膜多孔层的底部。结果表明,小电流镀铜能够使自腐蚀电位正移从而改善阳极氧化膜的耐蚀性。根据交流阻抗谱提出小电流镀铜后阳极氧化膜的等效电路。沉积铜对阳极氧化膜的改性作用使材料具有铜的电化学特性,是耐蚀性提高的根本原因。小电流镀铜处理与传统的电解着色工艺有本质区别,是一种新颖的提高阳极化铝合金耐蚀性的后处理方法。     

铝合金表面氧化膜对点焊电极磨损的影响

铝合金电阻点焊工艺中存在的一个主要技术难题就是电极磨损，探索铝合金点焊电极的磨损机理至关重要。研究了铝合金表面氧化膜对点焊电极磨损的影响，认为电极磨损，除了因为电极与铝合金工件接触面间的铜铝合金化以外。还因为电极与铝合金工件接触面间的不均匀点接触造成通电瞬间的局部爆炸而使铜电极表面产生局部塑性变形，从而引起铜电极表面局部区域的加工硬化，这种局部区域的加工硬化现象与铜铝合金化交互作用，使电极表面的脆化速度加快，电极磨损程度加重。     

微弧氧化膜对7050铝合金氢致局部塑性变形的影响

目的改善7050铝合金在湿空气中氢致延迟开裂敏感性高的问题,以延长其使用寿命。方法采用微弧氧化工艺在铝合金表面生成微弧氧化膜,研究微弧氧化膜对高强铝合金氢致局部塑性变形的影响。通过双悬臂梁(DCB)试样恒位移试验,评价微弧氧化膜对7050铝合金应力腐蚀敏感性的影响,通过读数显微镜原位观察和记录裂纹扩展情况。利用扫描电镜观察断口形貌,采用定氢仪分析氢含量。结果经过微弧氧化处理后,7050铝合金氢致局部塑性变形行为明显下降。测得有微弧氧化膜试样的应力腐蚀开裂门槛值KISCC为23.340MPa·m1/2,而无微弧氧化膜试样的KISCC为16.934MPa·m1/2。有膜的裂纹扩展速率为6.378×10–6 m/s,无膜的裂纹扩展速率为1.3612×10–5 m/s。同时微弧氧化膜使铝合金DCB试样中氢的体积分数从0.281×10–6下降到0.163×10-6。结论微弧氧化膜可以降低铝合金裂纹尖端的氢含量,从而抑制铝合金的氢致局部塑性变形。     

稀土元素在铝合金阳极氧化及其后处理工序中的应用

在铝合金阳极化溶液中加入稀土添加剂,能够提高氧化膜的耐蚀性能;将稀土盐用于铝合金氧化膜的封闭处理,效果也比较理想,因而稀土元素在铝合金表面处理领域中具有良好的应用前景。介绍了国内外善于稀土元素在铝合金阳极氧化及其后处理工序中的应用情况,并结合目前的研究现状,提出了今后研究中需要进一步探讨的问题。     

铝合金微弧氧化的研究进展

综述了微弧氧化技术的发展历程、成膜机理,论述了铝合金微弧氧化的特点。基于铝合金微弧氧化工艺研究现状,详细阐述了氧化时间、占空比、电压、电流密度、电解液浓度、基体粗糙度、纳米颗粒添加剂以及复合工艺等对铝合金微弧氧化膜层的组织与性能的影响。如电流密度会影响涂层的生长机理,使膜层的表面结构和内部缺陷产生较大的差异;采用不同的电解液所得到的膜层的厚度和粗糙度有明显的区别;在不同的电压参数下膜层的均匀性及膜层中微孔的尺寸大不相同;制备微弧氧化复合涂层以及采用纳米增强颗粒可使膜层的结构和性能有大幅提升。通过改变以上影响因素对铝合金微弧氧化膜层组织和结构加以调控,从而实现了对膜层性能的优化,如膜层的硬度、耐磨性、耐腐蚀性、抗疲劳性能的提高。最后对铝合金微弧氧化的发展方向提出了展望。     

预制膜对铝合金微弧氧化陶瓷层生长过程的影响

在磷酸盐体系电解液中,利用微弧氧化技术,分别对有、无高温氧化预制膜的铝合金进行表面陶瓷化处理,研究了预制膜对陶瓷层生长的影响规律.结果表明:高温氧化预制膜有利于提高陶瓷层的生长速率,降低起弧电压;陶瓷层的生长先是以初期形成的陶瓷颗粒为核心呈线状扩展,然后多条线接合呈网状,最后蔓延成面;陶瓷层生长的初期以高温氧化预制膜熔化生成为主,到后期,则是以铝合金基体熔化生成为主,此时预制膜对陶瓷层生长过程的影响较小,但由预制膜生成的陶瓷对陶瓷层生长的影响较大.     

7475铝合金微弧氧化后表面-界面能谱扫描分析

利用微弧氧化法在7475铝合金表面制备一层氧化膜,通过SEM、EDS、XRD等手段对其表面-界面形貌、化学元素组成和物相进行了分析,采用能谱仪对表面和结合界面进行了面扫描和线扫描分析,并用划痕法表征了氧化膜界面结合强度。结果表明,微弧氧化后7475铝合金表面形成一层粗糙多孔的氧化膜,其组成元素与氧化膜表面的物相相应分布;O原子以扩散形式与Al原子原位生长形成Al_2O_3,主要由α-Al_2O_3、γ-Al_2O_3组成,Si原子在表面氧化形成富集的Si-Al-O相;氧化膜厚度约为50μm,由间隙层、致密层和膜-基过渡层组成,与基体的界面结合强度为71.05 N。     

Development of porous anodic films on 2014-T4 aluminium alloy in tetraborate electrolyte

Anodic film growth on 2014-T4 aluminium alloy at 60 V in 50 g l⁻¹ di-sodium tetraborate at 60 °C has been examined by transmission electron microscopy and Rutherford backscattering spectroscopy. Initial film growth proceeds at relatively high efficiency on the initially etched and desmutted alloy. During the subsequent period of current decline, the reactive electrolyte species penetrate the outer film at preferred regions, establishing conditions for pore development by field-assisted dissolution. In the alkaline electrolyte, such field-assisted dissolution also appears to proceed locally, probably through mechanical disruption of the film, giving rise to a feathered film morphology. The oxidation of copper from the alloy, in the presence of an enriched layer of copper, developed largely by initial etching, also influences film morphology through parallel oxygen gas generation, creating oxygen-filled voids. Such gas-filled voids may rupture or be removed from the alumina film material through field-assisted dissolution at the pore base. In the former case, cracking allows access of the anodizing electrolyte to the enriched alloy/film interface, with subsequent dissolution of the enriched layer and local film growth; these give rise to lateral porosity in addition to that from pores passing perpendicularly to the alloy surface. The efficiency of anodizing is about 12%, with losses from Al³⁺ ion ejection, field-assisted dissolution, oxygen gas generation, film rupture, interface dissolution and local film repair.     

Incorporation of transition metal ions and oxygen generation during anodizing of aluminium alloys

Enrichment of nickel at the alloy/film interface and incorporation of nickel species into the anodic film have been examined for a sputtering-deposited Al-1.2at.%Ni alloy in order to assist understanding of oxygen generation in barrier anodic alumina films. Anodizing of the alloy proceeds in two stages similarly to other dilute aluminium alloys, for example Al-Cr and Al-Cu alloys, where the Gibbs free energies per equivalent for formation of alloying element oxide exceeds the value for alumina. In the first stage, a nickel-free alumina film is formed, with nickel enriching in an alloy layer, 2 nm thick, immediately beneath the anodic oxide film. In the second stage, nickel atoms are oxidized together with aluminium, with oxygen generation forming gas bubbles within the anodic oxide film. This stage commences after accumulation of about 5.4 × 10¹⁵ nickel atoms cm⁻² in the enriched alloy layer. Oxygen generation also occurs when a thin layer of the alloy, containing about 2.0 × 10¹⁹ nickel atoms m⁻², on electropolished aluminium, is completely anodized, contrasting with thin Al-Cr and Al-Cu alloy layers on electropolished aluminium, for which oxygen generation is essentially absent. A mechanism of oxygen generation, based on electron impurity levels of amorphous alumina and local oxide compositions, is discussed in order to explain the observations.     

Grain orientation effects on copper enrichment and oxygen generation during anodizing of an Al-1at.%Cu alloy

Anodizing of solid-solution Al-1at.%Cu alloy in ammonium pentaborate electrolyte is shown to develop two distinct types of amorphous film. On alloy grains of {1 0 0} orientation, the alumina film is of uniform thickness and relatively featureless. For other grains, the film is of non-uniform thickness and contains oxygen bubbles. In both cases, copper species are distributed throughout the film. Copper is enriched in the alloy to ∼5.8×10¹⁵ Cu atoms cm⁻² for bubble-free grains, with similar or slightly lower levels for other grains. Evidently, copper enrichment alone does not lead to generation of oxygen. Other factors suggested to be involved, each dependent upon grain orientation, are the structure of the enriched alloy layer, the cyclic nature of the oxidation of copper, and the generation of modulated film compositions.     

The behaviour of chromium during anodizing of Al–Cr alloys

The anodic oxidation of dilute Al–Cr alloys, containing 0.8 and 1.7 at% Cr, has been investigated in order to understand the oxidation behaviour of the alloying element and its influences on the film composition and morphology. The alloys reveal two stages of oxidation: an initial stage, in which only aluminium atoms are oxidized to form a chromium-free anodic alumina film, and a subsequent stage, in which both aluminium and chromium are oxidized, in their approximate alloy proportions, with generation of a chromium-contaminated anodic alumina film. In the first stage, chromium is enriched in a thin layer of alloy, immediately beneath the anodic film, to an amount corresponding to a layer of average thickness 1.5 nm and of average composition, Al–20 at% Cr. Following the oxidation of chromium, oxygen is produced electrochemically within the film at or near the alloy/film interface, probably associated with the development of chromium-rich clusters in the enriched alloy layer and, subsequently, formation of semiconducting chromium-rich oxide. Thus, the film material formed at the alloy/film interface by inward migration of O^2- ions contains many oxygen-filled bubbles with associated high pressures. The chromium species present in the film migrate outward more slowly than Al³⁺ ions. Hence, a layer of chromium-free anodic alumina, which thickens as the film grows, is maintained adjacent to the film/electrolyte interface.     

Influence of copper on the morphology of porous anodic alumina

Sputtering-deposited Al-Cu alloy layers and an Al-Cu/Al bi-layer are used to investigate the influences of copper on the morphology of porous anodic alumina films formed galvanostatically in either sulphuric or phosphoric acid electrolyte. The results reveal development of an irregular morphology of pores during anodizing of the alloy layers, contrasting with the linear porosity of films formed on aluminium. Further, the rates of film growth and alloy consumption are relatively low, since oxygen is generated following enrichment of copper in the alloy and incorporation of copper species into the anodic film. The linear morphology is re-established following depletion of the copper in the bi-layer and at the same time, film growth accelerates as oxygen evolution diminishes. The irregular pore morphology is considered to arise from stress-driven pore development influenced by effects of oxygen bubbles within the anodic alumina.     

Interactions of alloying elements during anodizing of dilute Al-Au-Cu and Al-W-Zn alloys and consequences for film growth

The anodizing behaviour of sputter-deposited Al-4 at.% Au-1 at.% Cu and Al-1.6 at.% W-0.6 at.% Zn alloys has been examined by Rutherford backscattering spectroscopy and transmission electron microscopy. Initially, a uniform, amorphous alumina film, free of copper and gold species, is formed on the Al-Au-Cu alloy; at the same time, a thin alloy layer, beneath the anodic film, is enriched in copper and gold. The uniform film growth is eventually terminated by generation of oxygen at gold-rich particles at, or near, the alloy/film interface, leading to bubble formation, subsequent rupture of the film and release of oxygen. Film growth on the Al-W-Zn alloy causes mainly enrichment of tungsten in the alloy, with the limited enrichment of zinc contrasting with the behaviour of Al-Zn alloys. Uniform film growth proceeds to high voltages with incorporation of mobile tungsten and zinc species into the film.     

铝合金表面SiO2陶瓷膜的研究

为了提高铝合金的表面硬度，增加其耐磨性，采用溶胶．凝胶法在铝合金表面制备了SiO2陶瓷表面膜，研究了乙醇、水、pH值和甲酰胺等相关工艺因素对溶胶性能及SiO2陶瓷表面膜的影响，以及SiO2陶瓷表面膜对铝合金表面硬度的改善情况。结果表明，通过控制相关工艺因素，可以在铝合金表面获得光滑平整的SiO2陶瓷表面膜，陶瓷表面膜能明显提高铝合金的表面硬度，浸涂7层SiO2陶瓷表面膜后，铝合金的表面硬度提高76％。     

Investigations into the relationship between the Corrosion behaviour of CN 108 alloy in sea water and the chemical composition of its corrosion products

This paper deals with the investigation of the corrosion behaviour of CN 108 alloy in sea water by means of surface analysis (SEM, EDS and XPS). The results with samples with different surface finishes (as-received or pickled), tested in natural or artificial sea water, are discussed. The chemical composition and the morphology of the corrosion products were established and realted to the corrosion behaviour of the alloy. In highly chlorinated sea water the growth of a cathodic film, strongly enriched in manganese, and pitting initiation at the grain boundaries, were observed on both as-received and pickled samples. The occurrence of general uneven corrosion in unchlorinated sea water is related to the presence of a surface film, strongly enriched in iron, which was neither protective nor homogeneous. The good performance of the alloy in intermediate chlorination conditions is related to the growth of a very compact, protective film, characterized by a balanced enrichment of both Fe and Mn.     

Structure and water-barrier properties of vanadate-based corrosion inhibitor films

Uniform, crack-free vanadium-based corrosion inhibitor films were grown on aluminum alloy 2024. Neutron and X-ray reflectivity were utilized to investigate the structure, water-barrier properties and speciation of the inhibitor film. The top part of the alloy participates in the formation of vanadate film. The similarity of films prepared from H₂O and D₂O implies the vanadate film is not hydrated. The film has a layered structure with vanadium enriched at the alloy interface. The film behaves as an effective water barrier when the thickness is greater than 800 Å. Films grown without K₃Fe[CN]₆ accelerator are found to be extremely thin.     

高熵合金CrNbTiVZr的微观组织及其在模拟PEMFC环境中腐蚀行为研究

采用真空电弧熔炼和热处理制备了CrNbTiVZr高熵合金,利用XRD、SEM/EDS、动电位与恒电位极化曲线测试及XPS表面分析等方法,研究了高熵合金铸态及退火后的微观组织特征以及合金在模拟PEMFC环境中的电化学腐蚀行为及其钝化膜组成。结果表明,CrNbTiVZr高熵合金的铸态和退火组织均由富集Ti、Nb元素的无序BCC相和富集Cr、V、Zr元素的Laves相组成。铸态和退火合金在模拟PEMFC阴极环境中腐蚀电流密度Icorr均比304SS不锈钢下降一个数量级,具有较好的耐蚀性和稳定性,但在阳极环境中其耐蚀性与304SS相当,其中铸态合金的稳定性较差。合金在阴极环境良好的耐蚀性主要与其表面形成由Cr2O3、Nb2O5、V2O3、Ti2O3及ZrO2组成的致密钝化膜关系密切。