纳米稀土氧化物对7075铝合金硬度和耐磨性的影响

对于超硬铝合金7075，本文通过加入纳米稀土氧化物来提高其硬度。在本次实验中加入纳米稀土氧化物的含量为0．2％，原铝合金7075和改性后的铝合金7075作硬度对比，结果加入纳米稀土氧化物的铝合金7075硬度较原铝合金7075提高22．4％。在干摩擦磨损测试中，加入纳米稀土氧化物的7075铝合金磨痕宽度比原铝合金7075小。     

Fabrication of Al-Mg-Re foams and their corrosion resistance properties

Al-2 wt.% Mg-Re foams with relatively small pore size (∼1 mm) were fabricated by the melt foaming method with the addition of titanium hydride as a blowing agent. The corrosion resistance properties of the Al-Mg-Re foams have been studied and the results compared with those of Al foam and Al-5 wt.% Cu foam. The results show that in order to get Al-Mg-Re alloy foams with good pore structures, Ca and Mg should be added to the pure Al melt before adding the blowing agent; the corrosion resistance properties of Al-Mg-Re foams are better than those of Al foam and Al-Cu foams.     

Corrosion inhibition of aluminum alloy AA 2014 by rare earth chlorides

The effect of LaCl₃ and CeCl₃ inhibitor additions in 3.5% NaCl solution on the corrosion behaviour of aluminum alloy AA2014 has been investigated. Four different concentrations (250, 500, 750 and 1000 ppm) of LaCl₃ and CeCl₃ were studied. The polarization resistance increased significantly and the corrosion rate decreased by an order of magnitude with the addition of 1000 ppm of LaCl₃ and CeCl₃, with maximum decrease noticed for CeCl₃. EIS studies showed that there was a significant increase in overall resistance after addition of 1000 ppm LaCl₃ and CeCl₃, when compared to the case without inhibitor. The double layer resistance and film resistance increased after inhibitor addition. Scanning electron microscopy confirmed formation of precipitates of oxide/hydroxide of lanthanum and cerium on cathodic intermetallic sites, which reduced the overall corrosion rate.     

稀土La及Sn对铸造铝合金组织、力学和阻尼性能的影响

研究了稀土La对含质量分数4%Sn铸造铝合金组织、阻尼和力学性能的影响,从La对Sn的形态和分布、La对Sn和铝合金基体润湿特性的影响等方面探讨了阻尼提高机制。结果表明,La含量为0.2%时,4%Sn的AlMgMnSi合金晶粒尺寸得到细化,β-Sn由大颗粒状变为细小、弥散分布,继续提高La含量至0.83%,晶粒变大,且在晶界处出现块状稀土化合物。La的加入可以有效提高含4%Sn铸造铝合金的阻尼性能,当La添加量为0.2%时,含4%Sn的AlMgMnSi和ZL102合金分别比不添加La的提高了约70%和100%。La改善了β-Sn与铝基体的润湿性,使β-Sn呈弥散、细小分布,从而有利于提高相界面阻尼,是本试样具有较高阻尼性能的主要原因。     

稀土Er改性AM50镁合金热挤压态的组织及耐蚀性能

通过ICP-AES、SEM、EDS分析、光学显微镜观察、电化学测试及腐蚀质量损失测定等方法研究了稀土Er改性铸造AM50镁合金经热挤压加工后的组织及耐蚀性能。结果表明,添加稀土Er后,组织中出现Al3Er和Al7ErMn5两个新相,减少了β-Mg17Al12相的数量,从而提高了AM50镁合金的耐蚀性能。腐蚀试验表明,热挤压加工的Er改性AM50镁合金表面腐蚀坑数量较多,但是蚀坑较浅,主要是由于热挤压加工导致了α-Mg的数量的增加。     

The influence of tensile stress on electrochemical noise from aluminum alloy in chloride media

An investigation was carried out on the potential features of 7075-T76 aluminum alloy under various constant stresses in 3.5% NaCl solutions. The applied stress accelerated the formation of electric double-layer at aluminum alloy/solution interface, and the formation time became shorter with the stress increasing. As the stress was applied, the fluctuating range and energy of potential noise improved in the low-frequency and reduced in the high-frequency while potential noise exhibited the characteristics of pitting corrosion. Potential fluctuation decreased gradually with time under loading. When the stress was released from the specimen, potential fluctuation weakened apparently, especially in the lower frequency range.     

La-Ce混合稀土对Mg-Al-Mn合金力学性能及耐蚀性能的影响

研究了La-Ce混合稀土对Mg-Al-Mn合金组织形貌、力学性能及耐蚀性的影响。采用T-1200CB坩埚炉冶炼稀土含量(质量分数)分别为4.63%、5.81%、6.18%的Mg-Al-Mn合金。在箱式电阻炉中对研究试样进行430 ℃保温24 h的固溶处理,然后进行200 ℃保温24 h时效处理。对不同热处理状态的试样进行组织观察,对固溶时效后的试样进行拉伸、硬度及盐雾腐蚀试验,从而分析La-Ce混合稀土对Mg-Al-Mn合金显微组织、力学性能及耐蚀性的影响。研究表明,随着合金中的La-Ce混合稀土含量的增加,Mg₁₇Al₁₂相逐渐被Al₄(La, Ce)相代替;硬度、抗拉强度和伸长率都逐渐减小,力学性能下降;合金的腐蚀速率逐渐下降,耐蚀性提高。     

The effect of corrosion inhibiting pigments on environmentally assisted cracking of high strength aluminum alloy

The effects of some corrosion inhibiting pigments on environmentally assisted cracking of 7075-T76 aluminum alloy were examined in 3.5% NaCl (pH=6.2) solution. In order to study the inhibition mechanism of these pigments in environmentally assisted cracking of aluminum alloy, electrochemical polarization tests were carried out in 3.5% NaCl (pH=6.2 and 3) and 0.1 M HCl solutions respectively with the presence and absence of these pigments. The results showed that the effects of the pigments on environmentally assisted cracking of aluminum alloy were exhibited mainly at crack initiation and the early stage of crack propagation. A nontoxic compound, composed of phosphate, molybdate, citrate, and thiazole/imidazole derivatives, was a promising pigment to inhibit environmentally assisted cracking of the alloy.     

Effect of combinative addition of strontium and rare earth elements on corrosion resistance of AZ91D magnesium alloy

The influencf of strontium（Sr） and rare earth（RE） elements on the corrosion behavior of AZ91D magnesium alloy was investigated by conventional corrosion testing and electrochemical measurements in 3.5% NaCl solution. After comparing the mass loss and hydrogen evolution of the samples, the microstructures of the alloys and the morphologies of their corrosion product films were characterized by electron probe microanalysis-energy dispersive spectrometry（EPMA-EDS） and Auger electron spectroscopy（AES）. Compared with individual addition of Sr or RE to AZ91D, the combinative addition of 0.5% Sr and 1% RE to AZ91D successfully decreases the corrosion rate further, which can be attributed to the depression of micro-galvanic couples, as well as the formation of more protective film due to aluminum enrichment. The combinative addition of strontium and rare earth elements to AZ91D magnesium alloy appears to be a promising approach to increase its corrosion resistance.     

Effects of rare earth metal addition on surface morphology and corrosion resistance of hot-dipped zinc coatings

Effects of rare earth metals (REM) addition on surface morphology and corrosion resistance of hot-dip galvanised steel were investigated. The corrosion resistance of steel samples galvanised with zinc and zinc alloys containing 0.05, 0.1, 0.2 and 0.5 wt.% REM were evaluated by various corrosion tests such as weight loss in salt spray chamber and natural sea water, sacrificial protection ability in contact with fog in salt spray chamber and after immersion in sea water, potential-time in sea water and linear polarisation in sodium chloride solution. Surface morphology and nature of the corrosion products were also investigated. The results indicated that the addition of small amounts of REM to the molten zinc galvanising bath can improve the corrosion resistance of hot-dip galvanised steel. Mechanisms by which the corrosion resistance of hot-dip galvanised steel are improved in presence of REM have been discussed.     

微量稀土对Al-Zn-Mg-Cu-Zr合金力学性能与腐蚀性能的影响

采用慢应变速率拉伸试验、显微硬度和电导率测试、晶间腐蚀和剥落腐蚀试验、光学显微镜、扫描电镜、透射电镜等分析方法,研究微量稀土对7085铝合金（Al-7.5Zn-1.5Mg-1.4Cu-0.15Zr）力学性能和腐蚀性能的影响。研究结果表明,与未添加稀土的合金相比,添加微量稀土使合金组织细化,时效后强度、硬度提高,电导率略有降低。同时,合金的耐腐蚀性大大提高,其中抗晶间腐蚀性能由四级提高为二级、48 h下的剥落腐蚀性能由EB提高为PA、反映应力腐蚀性能的ISSRT值由65%提高到96%。     

稀土对Zn-Al共晶合金超塑性的影响

采用恒速度法测量了稀土Zn-5Al共晶合金的塑性拉伸曲线, 结合金相组织研究了稀土对其超塑性特性的影响. 结果表明 在Zn-5Al合金中添加0.05%～0.2%(质量分数, 下同)的稀土Ce, 可提高合金超塑变形的延伸率, 在350℃以上进行超塑拉伸时, 稀土抑制Zn向Al中的扩散和溶解, 阻碍扩散溶解层达到饱和, 有利于α/β相界的滑移, 从而增强了Zn-5Al合金的超塑性效应.     

Zr与Er复合添加后的高Mg铝合金耐磨性能研究

Al-Mg系(5系)铝合金具有良好的加工性、耐腐蚀性和焊接性等,但中等硬度限制了其耐磨性的发挥。本研究在5系铝合金的主要元素Al-xMg-0.5Mn的基础上复合添加质量分数为0.14%Zr和0.35%Er,研究稀土高镁铝合金中(Mg含量最高达9.28%)Mg含量对其显微组织及摩擦磨损性能的影响。随着Mg含量从2.96%增加到9.28%,Al-xMg-0.5Mn-0.14Zr-0.35Er合金中形成的(Al, Mg, Mn, Er, Zr)复合白色相不断增多,尺寸不断增大,由棒条状变成细小鱼骨状,最后形成粗大鱼骨状。随着Mg含量从2.96%增加到9.28%,Er、Mg元素经常“相伴偏聚”,主要以Al(Er_xMg_1-x)和Al(Er_x(Mg, Mn)_1-x)相形式存在,由块状复合相转变成均匀分布的(Al, Mg, Mn, Er)复合相,具有一定强化作用,可显著改善合金摩擦磨损性能。复合添加0.14%Zr和0.35%Er后,合金的磨损方式从粘着磨损及磨粒磨损的混合磨损(Mg含量在2.96%～5.15%)转...     

稀土Sm对Al-7Si-0.3Mg合金微观组织的影响

采用金相显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和差示扫描量热法(DSC)等研究不同含量稀土Sm对Al-7Si-0.3Mg合金微观组织的影响。结果表明:添加Sm元素之后,合金的二次枝晶间距相比基础合金的明显减小;稀土Sm可以显著细化片层状的共晶硅,Sm元素主要形成Al2Si2Sm相。从能量角度,Sm可优先与P形成SmP相,可能会抑制AlP相的形成,减弱其促进共晶硅形核的效能。随着Sm元素含量的增加,Al-Si共晶反应的过冷度逐渐增大。     

Influence of rare earth metals on the characteristics of anodic oxide films on aluminium and their dissolution behaviour in NaOH solution

The characteristics of oxide films on Al and Al1R alloys (R = rare earth metal = Ce, Y) galvanostatically formed (at a current density of 100 μA cm⁻²) in borate buffer solution (0.5 M H₃BO₃ + 0.05 M Na₂B₄O₇·10H₂O; pH = 7.8) were investigated by means of electrochemical impedance spectroscopy. EIS spectra were interpreted in terms of an “equivalent circuit” that completely illustrate the Al(Al1R alloy)/oxide film/electrolyte systems examined. The resistance of the oxide films was found to increase on passing from Al to Al1R alloys while the capacitance showed an opposite trend. The stability of the anodic oxide films grown in the borate buffer solution on Al and Al1R alloys was investigated by simultaneously measuring the electrode capacitance and resistance at a working frequency of 1 kHz as a function of exposure over a period of time to naturally aerated 0.01 M NaOH solution. Analyses of the electrode capacitance and resistance values indicated a decrease in chemical dissolution rate of the oxide films on passing from Al to Al1R alloys.     

稀土镧对铝合金的去氢作用的机理分析

采用第一滴气泡法和减压凝固法 ,研究稀土镧对铝硅合金 (Al 11.2 %Si)中氢的作用 ,结果表明 :添加一定量的稀土镧 ,铝合金液体中溶氢量显著减少 ,铸件的针孔缺陷明显改善 ;稀土的去氢机理 ,认为稀土除氢效果不形成镧化氢 ,而主要是稀土镧减少氢在铝合金液体中的活度 ,降低铝合金液体中氢的析出压力 ,在凝固过程中增加氢在铝固溶体中有效分配系数。从热力学角度分析在铝液中形成镧化氢的条件。     

Filiform corrosion attack on pretreated aluminum alloy with tailored surface of epoxy coating

In the study, on the basis of material analysis of 6016 aluminum alloy widely used in Europe automotive industry, the influences of surface pretreatment on filiform corrosion and adhesion of epoxy coating/aluminum alloy interface were investigated, and the effect of rolling direction and coating property on filiform corrosion was also examined. The alloy surfaces were pretreated with etching solution, and then, respectively, with Aminopropyl silane solution, Aminopropyl phosphonate solution, and hexamethyldisiloxane plasma.The results showed that the susceptibility of pretreated surface to filiform corrosion was basically consistent with the distribution of intermetallic particles, and that water permeation and the tensility of coating were necessary for filament to grow. HMDSO plasma pretreatment could not only efficiently cover the matrix of 6016 aluminum alloy and cathodic intermetallic particles containing Al, Si, Mn, and Fe, but also apparently promote the adhesion of epoxy coating/aluminum alloy, as a result, the specimens with plasma pretreatment exhibited the superior performance in the filiform corrosion and peeling tests, so it was suitable to apply for the pretreatment of aluminum alloy in automotive industry.     

Effect of fluid hydrodynamics on flow-assisted corrosion of aluminum alloy in ethylene glycol–water solution studied by a microelectrode technique

Aluminum (Al) alloy microelectrodes were designed and installed in an impingement jet system to investigate the effect of fluid hydrodynamics on Al alloy corrosion in a flowing ethylene glycol–water solution by electrochemical measurements and computational fluid dynamics simulation. Results demonstrate that fluid hydrodynamics, in particular, the fluid flow velocity and shear stress, play an essential role in corrosion of Al alloy. The microelectrode located at the center of the sample holder is associated with the most stable state, while the one at the edge of the holder has the most active state. The electrochemical activity of the Al alloy microelectrode, indicated by the anodic dissolution current density, is directly related to the velocity of fluid flow and the shear stress.     

稀土Er对ZK21镁合金组织的影响

研究了添加稀土Er（0～4.0%）对半连续铸造ZK21合金铸态和均匀化态组织的影响。结果表明,稀土Er的添加可有效细化铸态组织,加入2.0%的Er使合金的平均晶粒尺寸由94μm细化至62μm,减小了34%。Er在均匀化态合金中部分固溶于基体中,部分与Mg、Zn元素形成热稳定Mg-Zn-Er三元化合物相;当稀土含量高于0.5%时,合金中不存在二元Mg-Zn相。随着稀土含量的增加,Er在基体中的固溶度增大,化合物的体积百分数增多,与此同时,Zn在基体中的固溶度减少。合金的硬度在Er含量为2.0%时达到最大,这是基体中Zn、Er元素固溶强化和析出相强化的综合作用结果。     

Microstructure and pitting corrosion of friction stir welded joints in 2219-O aluminum alloy thick plate

Effect of welding parameters on the microstructure and pitting corrosion of different positions along the thickness of weld nugget zone in friction stir welded 2219-O aluminum alloy plate was investigated using scanning electron microscopy (SEM), polarization experiment and electrochemical impedance tests (EIS). It was found that the material presents significant passivation and the top has best corrosion resistance compared to the bottom and base material. Corrosion resistance decreases with the increase of traverse speed from 60 to 100 mm/min at rotary speed 400 rpm. Corrosion resistance at rotary speed 600 rpm is lower than that at 500 rpm.