升温时效处理7075铝合金在含SRB模拟海水中的应力腐蚀行为

7系铝合金是一种可热处理强化的铝合金,通过改变热处理工艺的方法可以提高铝合金的抗应力腐蚀性能.本文研究了不同升温时效处理下,铝合金在含硫酸盐还原菌(SRB)模拟海洋溶液中的应力腐蚀行为,并通过应力-应变曲线和断口形貌,对比分析了铝合金在无菌溶液和SRB溶液中的应力腐蚀行为差异.研究表明,升温时效处理可以提高合金的自腐蚀电位,降低腐蚀电流密度和合金的应力腐蚀敏感性.硫酸盐还原菌(SRB)通过代谢促进了合金的腐蚀,改变了合金应力腐蚀开裂的机理,使合金的应力腐蚀开裂主要机理由阳极溶解转变为氢致开裂.     

7B04铝合金应力腐蚀敏感性研究

利用慢应变速率拉伸应力腐蚀实验方法研究7B04铝合金的应力腐蚀开裂敏感性。研究温度、腐蚀介质、电化学极化对应力腐蚀敏感性的影响,结果表明:随温度的升高7B04铝合金的应力腐蚀开裂敏感性增强;溶液的腐蚀性越强,7B04铝合金的应力腐蚀开裂敏感性越大;无论是阳极极化还是阴极极化都会增加7B04铝合金的应力腐蚀开裂敏感性。     

形变对LY12铝合金应力腐蚀开裂性能的影响

本文研究了不同的形变时效处理对LY12铝合金应力腐蚀开裂性能的影响。利用扫描电镜和透射电镜观察了各种形变时效状态试样应力腐蚀开裂的断口形貌及其微观组织,探讨了形变提高LY12铝合金应力腐蚀开裂抗力的原因。     

表面冲击改善铝合金搅拌摩擦焊接头应力腐蚀抗力的研究进展

铝合金广泛应用于航空航天、高速列车等新型装备,搅拌摩擦焊是这些装备的重要制造方法之一。然而,这些焊接结构在建造、服役过程中往往受到腐蚀环境的影响,在外力或残余应力耦合作用下极易发生应力腐蚀。诸多研究证实表面冲击技术可以提高铝合金的抗应力腐蚀性能,然而关于其防护机理尚处于推测阶段,至今没有统一定论。从应力腐蚀的力学因素和腐蚀因素两方面出发,剖析表面冲击对材料力学性能和耐腐蚀性能的影响,在此基础上,提出了表面冲击抑制铝合金应力腐蚀作用机制的研究方向,即通过构建关系模型定量表征改性层力学因素和腐蚀因素对接头应力腐蚀抗力的贡献率,可为阐明表面冲击抑制铝合金FSW接头应力腐蚀的关键因素及作用机理奠定基础,并为冲击工艺的优化提供理论支持。     

奥氏体不锈钢压力管道的应力腐蚀开裂及预防

在化工领域,输送腐蚀性介质的压力管道常用的材料为奥氏体不锈钢,而应力腐蚀开裂是奥氏体不锈钢压力管道最主要的失效方式。该文主要对奥氏体不锈钢压力管道应力腐蚀开裂的机理、主要影响因素及预防措施进行了分析讨论。分析发现:奥氏体不锈钢压力管道应力腐蚀开裂机理根据输送介质的不同可分为氢致应力腐蚀开裂和"滑移-溶解-断裂"模型;其腐蚀速率主要受拉应力、输送介质腐蚀性、运行温度、氢元素、输送介质对管壁的冲蚀等因素的影响;可通过采取合理选用材料及焊条、优化焊接工艺、避免产生应力集中点、防止腐蚀溶液富集、改变输送介质成分及运用阴极保护法等措施减缓应力腐蚀开裂的发生。     

7055铝合金T型型材的应力腐蚀行为研究

通过拉伸性能测试、C环应力腐蚀试验、金相分析、扫描电镜和透射电镜观察等研究了7055铝合金T型型材的应力腐蚀开裂(SCC)行为。结果表明:7055铝合金T型型材纵向试样的抗拉强度、屈服强度、伸长率及断面收缩率均大于横向试样的;在间浸腐蚀和恒温恒湿环境下,纵向C环试样的开裂时间均长于横向试样的。型材纵向截面晶粒变形特征明显,主要呈拉长状,横向试样的裂纹沿纵向扩展,裂纹一旦形成,沿着拉长晶界迅速扩展,裂纹平直,开裂时间短;型材横向截面晶粒呈等轴状,纵向试样的裂纹沿横向扩展,裂纹扩展过程中会沿着晶界发生偏折,开裂时间长。7055型材应力腐蚀机理为氢脆和电化学理论的共同作用。      

镁合金应力腐蚀机理及其影响因素分析

对近期国内外有关镁合金应力腐蚀的测试以及机理研究结果进行了分析,从腐蚀过程及动力学特征的双重角度分析了单纯电化学模式的不合理性,阐述了"化学引发-机械断裂","氢致开裂-机械断裂"两段式理论的主要观点.对影响镁合金应力腐蚀敏感性及可能导致其应力腐蚀开裂的各项因素进行了综合性讨论.指出了应力腐蚀机理研究亟待解决和应注意的问题.     

镁合金的应力腐蚀开裂:机理、影响因素、防护技术

随着节能、环保要求的日益提高,环境友好型结构材料的开发及应用受到越来越高的关注。镁合金由于对环境污染小、可回收利用率高等优点而极受世人青睐,成为21世纪最具发展前景的商用轻质材料,被广泛应用于航空航天、计算机、通讯等工业领域。然而,镁合金在应用过程中暴露出许多问题。由于镁活泼的化学性质导致镁合金在服役环境下极易受到腐蚀,例如在潮湿大气、海洋、含硫气氛中都能使镁合金发生点蚀、电偶腐蚀、晶间腐蚀等,使得镁合金结构件的整体或局部受到破坏。特别是在腐蚀和外力的双重作用下,镁合金将发生应力腐蚀开裂,导致结构件发生脆断。近年来,由于镁合金应力腐蚀开裂引起的结构失效案例逐年上升,造成了巨大的经济损失。目前,关于镁合金应力腐蚀开裂的研究主要集中于机理、影响因素和防护措施等方面。国内外学者相关研究表明,镁合金应力腐蚀开裂的机理总体上主要分为阳极溶解和氢脆两种理论,其中滑移溶解和氢局部增塑分别为两种理论的主流观点。但由于镁合金材料、服役环境的多样性以及力学、电化学腐蚀行为的复杂性,现有理论机理缺乏普遍适用性,且部分缺少直接实验验证,急需进一步系统研究。镁合金抗应力腐蚀性能受到镁合金服役环境、镁合金本身的加工工艺以及镁合金中的合金元素等诸多因素的影响。因此,依据应力腐蚀机理,结合影响因素,通过合理添加合金元素开发出新的镁合金,镁合金表面激光冲击改性或表面涂层,镁合金热处理、变质处理等方法都能够很好地降低镁合金应力腐蚀开裂的敏感性。特别是添加稀土元素,例如铒、铈等,能够使得镁合金组织优化,且能形成新的稀土相,对降低其应力腐蚀开裂敏感性的效果显著。本文系统归纳了镁合金应力腐蚀开裂的研究进展,分别对镁合金应力腐蚀开裂机理、影响因素以及其防护措施进行了论述,着重介绍了近十年来国内外的相关研究成果,并提出了镁合金应力腐蚀开裂领域未来的研究方向以及亟待解决的问题。     

电流互感器铝合金法兰开裂失效分析

某福建沿海地区用于电流互感器的铝合金法兰发生多处开裂,采用宏观检验、化学成分分析、金相分析、扫描电镜以及能谱分析等方法对该法兰开裂原因进行了分析。结果表明:法兰开裂均起始于螺栓孔处,为在腐蚀介质和应力共同作用下发生的应力腐蚀开裂;法兰螺栓扭紧力高、服役环境氯离子含量高以及法兰所用铝合金材料应力腐蚀开裂敏感性高等是造成该法兰开裂的主要原因。最后针对法兰开裂原因提出了预防措施。     

7A52铝合金焊接件应力腐蚀性能评价

应用慢应变速率拉伸应力腐蚀实验方法和恒载荷拉伸应力腐蚀实验方法评价了7A52铝合金焊接试样的应力腐蚀(SCC)敏感性,并对断口微观形貌进行了分析.结果表明:使用5A56焊丝,采用金属焊条惰性气体焊接(MIG)工艺双面焊制成7A52焊接件应力腐蚀敏感性比较低,具有较好的抗应力腐蚀开裂性能;但当使用环境温度较高、施加应力大于90％σp0.2时,也有可能发生应力腐蚀开裂.断口微观分析表明焊接部位普遍存在气孔;高温或高应力下产生SCC开裂的断口存在明显的二次裂纹,并且随着应力水平的增加,二次裂纹增大.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.