双级时效制度对6156铝合金组织和性能的影响

采用拉伸力学性能测试、电导率测定、晶间腐蚀实验及透射电镜分析等手段研究双级时效处理条件下6156铝合金的力学性能、电导率、晶间腐蚀和显微组织结构,采用正交实验优化双级时效工艺。结果表明:在本研究范围内,6156铝合金双级时效的四因素中第一级时效制度对合金的力学性能和电导率影响不大,第二级时效温度和时间是影响合金最终性能的主要因素。对于6156铝合金,最佳双级时效工艺为(175℃,6 h)+(210℃,5 h),相对于T6态,合金强度稍有降低,电导率上升,腐蚀类型也由晶间腐蚀转变为点蚀,腐蚀深度明显变浅。电镜观察结果表明:双级时效处理后,晶内析出大量的Q′相,晶界析出相球化且析出相之间的间距增大,呈断续分布,无沉淀析出带(PFZ)变宽,这种微观结构能有效提高6156合金的电导率和腐蚀性能,同时使合金具有较高的强度。     

电压对AZ31镁合金微弧氧化涂层微观结构及腐蚀性能的影响

为研究过程参数对镁合金微弧氧化涂层的微观结构及耐腐蚀性能的影响,在AZ31镁合金基体上,采用不同电压,在电解液磷酸三钠(Na3PO4)中制备微弧氧化涂层.采用扫描电子显微镜(SEM)及光学显微镜,分析膜层腐蚀前后的微观组织结构;通过X射线衍射仪(XRD)分析涂层样品腐蚀前后的相组成.采用动电位极化曲线和电化学阻抗谱(EIS)测试对涂层的耐腐蚀性能进行评价.结果表明:AZ31镁合金微弧氧化涂层主要由Mg3(PO4)2,MgO,Mg和少量MgAl2O4组成,腐蚀产物由Mg(OH)2,quintinite和Ca10(PO4)6 (OH)2组成.在电压为325 V,频率3 000 Hz,氧化时间为5 min下制备的微弧氧化涂层具有最致密均匀的微观形貌和最小的腐蚀电流密度,因此表现出最强的耐腐蚀性能.     

Monitoring corrosion rates and localised corrosion in low conductivity water

Monitoring of low corrosion rates and localised corrosion in a media with low conductivity is a challenge. In municipal district heating, quality control may be improved by implementing on-line corrosion monitoring if a suitable technique can be identified to measure both uniform and localised corrosion. Electrochemical techniques (LPR, EIS, crevice corrosion current) as well as direct measurement techniques (high-sensitive electrical resistance, weight loss) have been applied in operating plants. Changes in the corrosion processes are best monitored in non-aggressive, low conductivity media with sensitive electrical resistance technique and crevice corrosion current measurements.     

镁与热处理对Al-4Si-(xMg)合金导电性及力学性能的影响

利用SEM、XRD、EDS、硬度计及电阻率测试仪等方法分析Mg元素和不同热处理对Al-4Si-(xMg)(x=0～1.5％,质量分数)系列合金导电率及硬度的影响.结果表明:随Mg添加量增加,铸态合金的导电率和硬度先增后减,最佳添加量为1.1％.Mg使铸态合金硬度显著增加,但恶化了其导电率.Al-4Si-(xMg)合金经...     

Investigation of the relationship between intergranular corrosion and retrogression and reaging in the AA6063

AA6063 was heat treated with different retrogression temperatures and durations, and the effect of heat treatment conditions on the microstructure, hardness, electrical conductivity, intergranular corrosion (IGC) and electrochemical corrosion behaviours of the AA6063 was determined compared with the T6 condition. The IGC test was applied according to the BS EN ISO 11846: 2008 standard. Moreover, potentiodynamic polarization tests were applied to determine the electrochemical corrosion behaviour of the heat‐treated samples. Electrochemical corrosion tests were carried out by using a Ivium Compactstat potentiostat in 3.5 wt.%. NaCl solution at 24°C with a scanning rate of 0.5 mV/s. The corrosion test cell consisted of the reference electrode (Ag/AgCl), working electrode (test sample) and a reference electrode (platinum). The effect of IGC on the microstructure of AA6063 and corrosion depth values was investigated by using a stereo optical microscope and a light metal microscope, respectively. Corrosion depth examinations were performed on microstructures taken from the cross‐sections of the samples. The chemistry of the precipitates formed at grain boundaries and distribution of the precipitates in the microstructure were investigated by scanning electron microscope, energy dispersive X‐ray and transmission electron microscope analyses. The results showed that retrogression and reaging heat treatment improves both the corrosion resistance and the mechanical properties of AA6063. After 50°C/15 min RRA heat treatment, the highest corrosion resistance and a higher hardness value than the T6 level were obtained.     

Aqueous Corrosion Behavior of Micro Arc Oxidation (MAO)-Coated Magnesium Alloys: A Critical Review

Magnesium (Mg) and its alloys, in the current era of persistently growing engineering demands, have become the most promising materials finding widespread industrial applications. Numerous processes are available for surface protection of Mg and its alloys to potentially minimize corrosion damage. The micro arc oxidation (MAO), a fairly recent and eco-friendly coating process, emerged as a novel means to provide an adherent, hard, scratch-resistant, wear-resistant, and corrosion-resistant coatings on Mg alloys. However, the successful utilization of such coatings demands a thorough understanding of the influence of a relatively large number of process parameters such as electrolytic composition, presence of insoluble additives in the electrolyte, electrical parameters employed, and the composition of the Mg alloy substrate on the corrosion resistance. The detailed influence of all the above parameters on the corrosion behavior of Mg alloys is critically reviewed and presented in this article. In addition, this article also reviews the recent trends in terms of duplexing the MAO process using different techniques/processes such that the composite coatings are produced with enhanced corrosion resistance.     

电场激活合成Mg2Si的热电性能研究

用Mg粉和Si粉通过电场激活加压辅助法（Field-activated and Pressure-assisted Synthesis,FAPAS）,在1073 K、50 MPa条件下快速实现了Mg2Si块体热电材料的一步法合成与致密化;合成过程反应物反应完全,产物的XRD曲线的Mg2Si峰型尖锐,占产物含量的99.5%。合成样品的Seebeck系数、电导率、功率因子分别在562K、773 K、600 K时达到最大值,分别为445μVK-1、54.4 Scm^-1、4.35 W/cmK^2。通过对比多种方法合成的Mg2Si热电材料的热电性能发现,FAPASA样品的功率因子比其它方法具有明显的优势。     

Corrosion behavior of novel Cu–Ni–Al–Si alloy with super-high strength in 3.5% NaCl solution

A novel Cu–6.5Ni–1Al–1Si–0.15Mg–0.15Ce alloy with super-high strength was designed and its corrosion behavior in 3.5% NaCl solution at 25 °C was investigated by the means of SEM observation, TEM observation and XPS analysis. The alloy after solution treatment, 80% cold rolling and aging at 450 °C for 1 h had the best comprehensive properties with hardness of HV 314, electrical conductivity of 19.4% IACS, tensile strength of 1017 MPa, and average annual corrosion rate of 0.028 mm/a. The oxides and chloride products formed at first, followed by the formation of dyroxides products. The alloy showed super-high strength, good electrical conductivity and corrosion resistant because Ni₂Si hindered the precipitation of large NiAl at the grain boundary and the denickelefication of the alloy.     

含石墨烯胞室结构的铜复合材料及其耐腐蚀性能

目的 开发一种石墨烯在铜基复合材料中的均匀分散结构,制备出兼具高导电和强抗刻蚀性能的石墨烯/铜复合材料。方法 采用化学气相沉积原位生长法结合分散剂工艺,制备分散均匀石墨烯/铜基粉体复合材料。利用制备的石墨烯/铜粉体材料,采用真空热压工艺,制备了石墨烯/铜块体材料,然后用拉曼光谱、X射线粉末衍射仪和金相显微镜,考察石墨烯/铜试样的质量和形貌,最后用数字便携式涡流电导仪测量其电导率。利用自主设计的石墨烯/铜在过硫酸铵中刻蚀的实验装置,测试石墨烯/铜的抗刻蚀性能。结果 利用石墨烯/铜粉体制备的石墨烯/铜块体和铜具有相同的(111)、(200)和(220)晶面,多层石墨烯以立体胞室结构均匀分布在铜晶粒的晶界处。石墨烯/铜块体的导电率为96%IACS,明显优于文献报道的以其他方法制备的石墨烯/铜块体,并且在过硫酸铵溶液中浸泡90 min后,石墨烯/铜块的质量损失为126.6 mg, 石墨烯/铜比纯铜的抗刻蚀能力提高了37.6%,具有比铜更强的抗刻蚀性能。结论 以CVD原位生长法和真空热压法制 备的石墨烯/铜复合材料,石墨烯以立体胞室结构均匀分散在铜界面处,并且兼具高的导电性和强的抗刻蚀性能。     

镁合金表面制备高红外发射率和高导电率热控膜层

目的通过电沉积方法在镁锂合金表面制备具有高红外发射率以及高导电率的镀层,满足其在太空中散热以及电磁屏蔽的需要。方法通过前处理工艺(碱洗→酸洗→预钝化→化学镀镍磷→电镀铜)提高镁锂合金基体的耐蚀性能以及与后续镀层的结合力,并在此镁锂合金前处理工艺的条件下,电沉积多孔Zn-Ni合金镀层。通过热循环测试和电化学方法评价各镀层的电化学腐蚀行为和各镀层之间的结合力。结果各镀层之间的结合力良好,化学镀Ni-P层、电镀Cu层和多孔Zn-Ni层的耐蚀性能均优于镁锂合金基体,该组合镀层的协同作用可以有效地保护镁锂合金基体,提高其耐蚀性。结论最外层多孔Zn-Ni合金镀层主要由Ni2Zn11、NiO、NiS组成,其红外发射率为0.90,电阻率小于0.01 m?/cm。这表明多孔结构可以有效提高金属合金镀层的红外发射率,并保持合金镀层的高导电性。     

Four-terminal measurement of the distribution of electrical resistance across stress corrosion cracking

This study measures electrical resistance of a stress corrosion crack directly by the four-terminal method to discuss appropriate modeling from the viewpoint of electromagnetic nondestructive evaluation. Two type-316 stainless steel plate specimens containing artificial stress corrosion cracks were prepared, and columnar samples containing penetrating cracks were cut from the plates for the measurements. The results obtained agree with recent reports discussing appropriate numerical modeling of stress corrosion cracking on the basis of finite element simulations. In contrast, this study also reveals that it is not always valid to assume that a stress corrosion crack has uniform conductivity internally.     

Yb_2O_3掺杂对15(20Ni-Cu)/(NiFe_2O_4-10NiO)金属陶瓷性能的影响

采用冷压-烧结技术制备NiFe2O4-10NiO基金属陶瓷材料;通过对烧结体的显微结构和物相组成、电导率、电解试样的表层形貌、电解质和阴极铝的杂质增量等的分析检测,研究Yb2O3掺杂对15(20Ni-Cu)/NiFe2O4-10NiO金属陶瓷致密度、导电率和耐腐蚀性能的影响。结果表明:1 300℃烧结的0.5%Yb2O3-15(20Ni-Cu)/(NiFe2O4-10NiO)金属陶瓷具有较好的性能,相对密度为98.53%,960℃时的电导率为53.06 S/cm,电解腐蚀后金属腐蚀层厚度为20~30μm,总杂质增量为0.079 g。     

具有高耐蚀性和导电性的掺Cr类金刚石非晶碳的化学式解析

Cr掺杂的类金刚石非晶碳具有良好的导电性和耐腐蚀性,这对于燃料电池金属双极板涂层改性特别重要。使用团簇加连接原子模型对其非晶结构进行了详细解析,在该模型中,良好的玻璃形成材料由覆盖特征性最近邻团簇加上几个下一壳层原子的结构单元来表述。根据文献,在Cr掺杂的类金刚石非晶碳中占优势的团簇是Cr中心和C壳层的[Cr-C4]四面体团簇,然后将该团簇与适当的连接原子匹配,以满足电子轨道饱和原理。由此推导出了两个最优组成式,即[Cr-C4]CrC3(22.2%Cr)和[Cr-C4]Cr3C2(40%Cr),它们显示出良好的非晶态结构稳定性。实验结果显示,所提出的这两组化学组成的涂层材料兼具低电阻率(低至10-4Ω·cm)和优异的耐腐蚀性(腐蚀电流密度~10^-2μA/cm^2)。在sp2键含量和渗流理论的框架内讨论了导电和耐蚀的协同行为。这项工作验证了团簇加连接原子模型在具有高耐腐蚀性和高导电性的涂层材料成分设计中的可行性。     

Corrosion Resistance of Copper Coatings Deposited by Cold Spraying

In the article, a study of corrosion resistance of copper and copper-based cermet (Cu+Al₂O₃ and Cu+SiC) coatings deposited onto aluminum alloy substrate using the low-pressure cold spraying method is presented. The samples were subjected to two different corrosion tests at room temperature: (1) Kesternich test and (2) a cyclic salt spray test. The selected tests were allowed to simulate service conditions typical for urban, industrial and marine environment. Examination of corroded samples included analysis changes on the coating surface and in the microstructure. The physicochemical tests were carried out using x-ray diffraction to define corrosion products. Moreover, microhardness and electrical conductivity measurements were conducted to estimate mechanical and physical properties of the coatings after corrosion tests. XRD analysis clearly showed that regardless of corrosion conditions, for all samples cuprite (Cu₂O) was the main product. However, in the case of Cu+Al₂O₃ cermet coating, chlorine- and sulfate-containing phases such as Cu₂Cl(OH)₃ (paracetamite) and Cu₃(SO₄)(OH)₄ (antlerite) were also recorded. This observation gives better understanding of the lowest microstructure changes observed for Cu+Al₂O₃ coating after the corrosion tests. This is also a justification for the lowest decrease in electrical conductivity registered after the corrosion tests for this coating.     

开孔泡沫铝导电性的研究

本文采用加压渗流方法制备开孔结构的泡沫铝,并通过调整工艺参数改变泡沫铝的孔径和相对密度.采用“直流四端电极”法测量了不同参数泡沫铝的电阻,研究开孔泡沫铝的导电性随其相对密度和孔径的变化规律.实验结果表明：随着相对密度的提高,开孔泡沫铝的电导率增大,且电导率随相对密度的改变呈指数关系变化;当相对密度参数基本相同时,随着泡沫铝孔径的减小,由于在制备过程中产生的结构缺陷增多,其电导性下降.     

Mg含量和冷速对Mg-Cu-Zn-Y非晶复合材料微观结构及腐蚀行为的影响

采用水冷铜模法和水淬法制备得到Mg65+x(Cu0.66Y0.34)30-xZn5(x=5,10,15)非晶及其复合材料。并通过XRD、SEM对材料结构进行表征,研究Mg含量和冷却速度对样品微观结构的影响。结果表明:由水冷铜模法得到的x=5样品为单一非晶,x=10和15样品是由非晶相与Mg固溶体相组成的非晶复合材料。而利用冷速较低的水淬法得到的样品为非晶复合材料,其主要由Mg,Mg2Cu,MgZnY和非晶相组成。通过研究合金在NaCl中性溶液中的腐蚀行为,发现随着Mg含量的增加,样品的耐腐蚀性能有所下降。并且对于同成分的合金,由冷速较快的水冷铜模法得到的样品耐蚀性相对较好。     

Effects of retrogression and reaging heat treatment on the microstructure,exfoliation corrosion,electrical conductivity,and mechanical properties of AA7050

The effects of different retrogression times and temperatures on the microstructure, electrical conductivity, exfoliation corrosion (EXCO), and hardness of the 7050 aluminium alloy were compared with the T6 and T7451 condition. The EXCO solution was prepared in accordance with ASTM G34‐01 standard and the samples were kept in the solution for 48 hr. Corrosion depths were examined by using scanning electron microscope (SEM) in the cross‐sections microstructure of the samples. The effect of EXCO on the material was investigated using stereo optical microscope images. In microstructure investigations, SEM and energy dispersive X‐ray (EDX) analyses were used to determine the distribution and chemistry of the precipitates at the grain boundaries. The results show that retrogression and reaging (RRA) times and temperatures have significant effects on AA7050 EXCO. Especially after 200°C/30 min RRA process, it has been found that 7050 aluminium alloy has higher mechanical strength than T6 level and high corrosion resistance from T7451 level. According to the results of this study, it has been shown that there is a direct connection between electrical conductivity and EXCO.     

Ni元素对非晶合金Mg_(65)Cu_(25)Gd_(10)在NaCl溶液中腐蚀行为的影响

采用析氢腐蚀实验比较了非晶合金Mg65Cu25Gd10和Mg65Cu20Ni5Gd10在1%NaCl溶液中腐蚀性能。利用电化学测试技术和场发射扫描电子显微镜(FESEM)对两非晶合金在NaCl溶液中的腐蚀行为进行了研究。析氢腐蚀实验表明,Ni的加入大大提高了非晶合金Mg65Cu25Gd10抗蚀性能,极化曲线测试结果也表明Mg65Cu20Ni5Gd10非晶合金的腐蚀电流远远小于Mg65Cu25Gd10非晶合金。EIS测试表明,电化学阻抗谱测试结果显示Mg65Cu20Ni5Gd10非晶合金电荷转移电阻高于Mg65Cu25Gd10非晶合金。腐蚀产物形貌观察表明,Ni的加入使非晶合金Mg65Cu20Ni5Gd10腐蚀表面膜更为致密。结合各测试结果,探讨了Ni的加入提高镁基非晶合金耐蚀性机理。     

Development of Slippery Liquid-Infused Porous Surface on AZ31 Mg Alloys for Corrosion Protection

The relatively poor corrosion resistance remarkably limits the wide applications of Mg alloys in practice, although they possess many attractive properties, like low density, high specific strength, and good biocompatibility. The formation of a protective coating can effectively suppress the corrosion. In this work, a slippery liquid-infused porous surface (SLIPS), with good surface hydrophobicity, stability, and self-healing property, was formed on AZ31 Mg alloys. The development of SLIPS requires suitable porous micro/nanostructures. Layered double hydroxide (LDH), with effective corrosion resistance for Mg alloys, was a good candidate to accommodate the liquid lubricant. Especially, different temperatures were applied to in situ form MgAl-LDH on AZ31 Mg alloys. The results showed that the temperature of 120 °C was the best condition for the SLIPS to provide good corrosion protection for Mg alloys, with the lowest corrosion current density of 3.19 × 10^-9 A cm⁻². In addition, the SLIPS performed well in the long-term immersion test and abrasion test. The AZ31 Mg alloys with superior corrosion resistance and good mechanical and chemical stability can be extensively applied in areas of automotive, electronics, and aerospace.     

铝合金双极板磁控溅射Ag掺杂类石墨薄膜表面改性研究

目的研究在铝合金样品表面制备Ag掺杂类石墨薄膜对样品导电、耐蚀性能的影响。方法采用磁控溅射离子镀技术,在6061铝合金表面沉积了Ag掺杂类石墨层,对样品微观形貌、接触电阻和电化学腐蚀性能进行了观察测试。结果类石墨薄膜厚度随着Ag靶电流的提高而增大。与铝合金基体相比,镀膜样品的接触电阻降低了2个数量级,腐蚀电流密度降低了2~3个数量级。Ag靶材电流为0.04 A时,镀膜样品接触电阻(1.5 MPa压强)为1.93 m?·cm~2,腐蚀电流密度低至10~(-5.5) A/cm~2数量级。结论沉积有Ag掺杂类石墨薄膜的样品达到了极低的表面接触电阻与较低的腐蚀电流密度,使镀膜后的铝合金样品具有优异的导电性能与较好的耐腐蚀性能。