冷加工对含Mn铝合金管腐蚀行为的影响

采用SEM,TEM,动电位极化和浸泡实验研究了机械冷加工变形对汽车散热器高Mn(0.22%,质量分数,下同)和低Mn(0.08%)铝合金管在0.6 mol/L NaCl(pH=6)和SWAAT(ASTM G85,pH=3)溶液中的腐蚀行为的影响.电化学极化测试表明,无形变时高Mn铝合金直管的点蚀电位最高;但冷加工能降低高Mn铝合金弯曲表面的点蚀电位,而对低Mn铝合金的点蚀电位没有明显影响.TEM观察发现,冷加工后高Mn铝合金中有大量纳米尺度的富Mn析出相,在低Mn铝合金中却没有观察到这种析出相,阴极极化测试表明,富Mn相能显著促进阴极反应,富Mn相相对Al基体为阴极相,因而是点蚀萌生的部位.添加Mn尽管有利于提高铝合金的耐蚀性,但机械冷加工会弱化这一效应.     

热处理对6063铝合金组织与性能的影响

利用金相显微镜观察经固溶、时效及固溶+时效处理的6063铝合金的显微组织,通过测试其硬度,得出其随温度变化的规律;并通过全浸腐蚀试验比较其耐腐蚀性,观察其在不同温度下的腐蚀形貌.结果表明,经不同温度处理的材料其显微组织发生明显改变,硬度随温度呈一个波动趋势,随温度升高其耐蚀性下降.     

7A52铝合金搅拌摩擦焊焊缝的电化学局部腐蚀行为

7A52铝合金搅拌摩擦焊焊缝的成分虽然与母材相同,但其经历了再结晶过程和特殊的热处理过程,粗大第二相发生的变化会导致其电化学行为发生改变.文中分析了焊缝的显微组织和粗大第二相,对母材和焊缝分别进行了电化学测试,并观察了腐蚀后的表面形貌和特征,以确定局部腐蚀形核处.研究结果表明,焊缝的电化学局部腐蚀过程与母材相似,均为Mg2Si优先阳极溶解,产生自身的点蚀坑,随着腐蚀的进行,Mg2Si周围的基体被腐蚀.而a-Al12(Fe,Mn)3Si与Al6(Mn,Fe)并未被腐蚀.     

5A06铝合金搅拌摩擦焊接接头的金属流动规律,显微组织以及腐蚀行为研究

对5A06铝合金在搅拌摩擦焊接过程中的金属流动规律以及焊后显微组织演变和腐蚀行为进行研究。结果表明:由于受到扭转和漩涡运动的综合作用,前进侧金属被直接卷入搅拌针的螺纹内部,然后被向下挤压进入焊核区。然而,后退侧的金属展现出无序的金属流动模式。通过扫描电子显微镜电子背散射分析发现,搅拌区的晶粒在动态再结晶的作用下发生了明显的细化,再结晶后平均晶粒尺寸约为6μm。对搅拌区的扫描电子显微分析结果表明,β相(Al_3Mg_2)和Al6(Mn,Fe)呈弥散分布,且和母材相比Al6(Mn,Fe)颗粒明显细化。同时,焊缝截面的硬度分布表明焊后5A06铝合金具有软化趋势,最小硬度值(HV)为720 MPa,位于搅拌区和热机影响区的界面处。通过电化学分析和浸泡后的组织观察发现搅拌区的耐腐性明显优于母材,母材的腐蚀电位为–0.725 V,而搅拌区域腐蚀电位升高35 mV。     

15Mn钢在3.5%氯化钠水溶液中的腐蚀疲劳

研究了不同组织状态的15Mn钢在3.5％氯化钠水溶液中的疲劳裂纹扩展行为,测定了裂尖区的平均氢含量和裂纹闭合力,发现外部条件(力学及环境)和材料的显微组织对腐蚀疲劳有重要影响。结合断口和裂纹走向观察,提出了15Mn钢腐蚀疲劳断裂的复合机制和断裂机制图。     

铝合金散热器腐蚀失效分析

采用宏观检测、化学成分分析、力学性能试验、显微组织观察等方法,对铝合金散热器漏水失效的原因进行了综合分析。结果表明:散热器管内漆膜存在涂覆不均匀、堆积、气泡、鼓泡等质量问题,无法有效地隔绝循环水与铝合金基体接触,使铝合金基体优先在内漆膜缺陷处发生局部腐蚀,并在循环水的冲刷作用下,加速腐蚀,最终造成散热器管的腐蚀穿孔。     

回归再时效对6082合金组织及电化学腐蚀性的影响

采用电化学方法研究了经不同回归再时效工艺处理的6082铝合金在3.5%的NaCl溶液中的腐蚀行为,通过显微组织、XRD和极化曲线分析发现,6082铝合金组织为α-Al基体上均匀分布且取向明显的β-Mg2Si颗粒及单质Si;回归处理后铝合金基体中几乎没有强化相,再时效晶内析出细小弥散的强化相,晶界上形成粗大断续状的平衡态组织。回归工艺为220℃×40min与220℃×60min时可以提高6082铝合金耐电化学腐蚀性能。     

固溶时效处理对AlMg5Si2Mn铝合金组织与性能的影响

利用硬度测试、显微组织观察、XRD、拉伸性能测试及断口截面组织观察等表征手段研究了固溶时效处理对AlMg5Si2Mn铝合金组织与性能的影响。结果表明,AlMg5Si2Mn铝合金固溶时效处理后的组织中Mg₂Si形貌发生改变,从迷宫状和棒状转变为细小圆球状,分布更为均匀,并且铝合金的硬度显著提高,还随固溶温度的升高而先增加后降低,同时拉伸性能亦有显著提高。经530℃×30 min固溶和190℃×6 h时效后,合金的硬度较高,为49.5 HRB,抗拉强度、屈服强度和断后伸长率分别为260 MPa、173 MPa和17%。     

机加工AA7150铝合金的抗丝状腐蚀性能（英文）

采用扫描及透射电子显微技术表征机加工AA7150铝合金近表面变形层的显微组织,并结合动电位极化曲线及丝状腐蚀测试研究机加工后AA7150铝合金的丝状腐蚀行为。研究发现,机加工后AA7150铝合金近表面区域出现晶粒细化、合金元素重新分布以及晶界偏析等特征。机加工过程中强烈的塑性变形导致近表面区域显微组织的改变,从而极大地提高合金近表面变形层的腐蚀倾向。机加工使合金表面粗糙度增大,并导致形成电化学活性明显提高的近表面变形层。在二者共同影响下,机加工后AA7150铝合金的抗丝状腐蚀性能明显下降。     

2219铝合金晶界镓浸润工艺研究

基于液态镓沿着铝合金基体晶界发生浸润的现象,提出一种新颖的揭示铝合金基体晶界的方法——渗镓法金相观察技术。分别对等轴晶态、时效态和轧制态的2219铝合金样品进行渗镓处理,然后利用金相显微镜(OM)和电子探针显微分析(EPMA)观察铝合金基体晶界显示的情况。结果表明,通过适当的渗镓工艺处理,三种状态2219铝合金样品铝基体显微组织上晶界清晰完整,显现的效果优于传统方法(机械抛光+腐蚀法、阳极覆膜法)的;渗镓处理后铝合金基体在金相显微镜下的成像质量更高。     

On a new concept of rotary draw bend-die adaptable for bending tubes with multiple outer diameters under non-mandrel condition

A traditional rotary draw bending die on the numerically controlled (NC) tube benders or other benders can bend tubes with only one kind of outer diameter. It is difficult for such a situation to meet the requirement of modern manufacturing with characters of much varieties and small batch. The present study proposed a new concept of rotary draw bending die called MDB-Die (Multiple-diameter Bending Die), on which tubes with different outer diameters within a definite range can be bent using the same die by only adjusting the pads inside the die set. Numerical and experimental approaches were employed to investigate the forming process of tubes with different outer diameters when bent on the MDB-Die, especially on the characters of force and elastic-plastic deformation of tube wall, and the effects of groove shapes and bending parameters on the cross-section distortion and wall thinning in the process. Analytical expressions in simple tube bending based on plastic theories given by Tang (2000) for calculating the magnitude of stresses, together with the wall thickness change, deviation of the neutral axis, and section flattening, were also used for comparison. The result proved that tubes with different outer diameters (from 18 to 25 mm in the study) can be bent successfully on MDB-Die without degrading the bending quality, i.e., the aspect ratios of section distortion of less than 5% and wall thinning of less than 7.8%.     

Corrosion of NiTi Wires with Cracked Oxide Layer

Corrosion behavior of superelastic NiTi shape memory alloy wires with cracked TiO₂ surface oxide layers was investigated by electrochemical corrosion tests (Electrochemical Impedance Spectroscopy, Open Circuit Potential, and Potentiodynamic Polarization) on wires bent into U-shapes of various bending radii. Cracks within the oxide on the surface of the bent wires were observed by FIB–SEM and TEM methods. The density and width of the surface oxide cracks dramatically increase with decreasing bending radius. The results of electrochemical experiments consistently show that corrosion properties of NiTi wires with cracked oxide layers (static load keeps the cracks opened) are inferior compared to the corrosion properties of the straight NiTi wires covered by virgin uncracked oxides. Out of the three methods employed, the Electrochemical Impedance Spectroscopy seems to be the most appropriate test for the electrochemical characterization of the cracked oxide layers, since the impedance curves (Nyquist plot) of differently bent NiTi wires can be associated with increasing state of the surface cracking and since the NiTi wires are exposed to similar conditions as the surfaces of NiTi implants in human body. On the other hand, the potentiodynamic polarization test accelerates the corrosion processes and provides clear evidence that the corrosion resistance of bent superelastic NiTi wires degrades with oxide cracking.     

新型弯管综合测量检具设计

设计了一种新型弯管检具,对检具的设计作了详细说明。该检具适用于多基准、高精度的弯管件检验,在检验过程中收到了很好的效果,为控制弯管质量提供了保障。     

弯曲加载对油井管应力腐蚀敏感性的影响

采用四点弯曲试验，研究拉应力对油井管抗SSCC性能的影响，加载比例分别为0、50%、80%和90%，利用OM、LCSM、EPMA等分析手段研究加载比例对油井管试样的微观腐蚀形貌和腐蚀深度的影响，分析锈层横截面形貌和元素分布情况。结果表明：油井管的金相组织为回火索氏体；弯曲加载使点状腐蚀坑沿垂直于拉应力的方向扩展，由点状逐渐变成长条状，随着加载比例的增加，腐蚀坑的长度和深度逐渐增加，相邻的点蚀坑聚集形成更大的腐蚀坑，应力腐蚀敏感性增强；Cr和Mo促使锈层致密，阻碍H原子的扩散和S离子迁移，提高了抗应力腐蚀性能。     

某输气管线弯管开裂原因分析

某弯管发生刺漏现象,为明确该弯管开裂原因及失效机理,本文采用宏观分析、理化性能、微观分析、腐蚀模拟试验等手段对其进行分析研究.结果表明:该弯管开裂失效机理为硫化氢应力腐蚀,失效的主要原因为,该弯管热煨弯工艺不合理,导致弯曲段产生大量的马氏体组织,马氏体组织硬度较高,对硫化氢应力腐蚀开裂较为敏感;该弯管输送的天然气中含有...     

水冷壁管受热面失效分析

通过电子探讨,能谱和Ｘ射衍射等多种分析技术系统分析某电厂锅炉水冷壁管发生局部腐蚀的原因。结果表明,腐蚀产物中硫含量很高,局部区域超过２０（ｗｔ％）,产物主要由铁的氧化物和硫化物组成。水冷壁管受热面腐蚀主要原因是高温硫腐蚀。     

燃煤火电厂锅炉“四管”的高温腐蚀

燃煤火电厂锅炉的高温腐蚀主要发生在受热面的“四 管”,即水冷壁管、过热器管、再热器管和省煤器管.腐蚀的主要类型是硫腐蚀、氯腐蚀、 水蒸汽腐蚀和钒腐蚀.本文综述了燃煤火电厂锅炉存在的典型高温腐蚀现象和机理,并简要 的介绍了一般防腐蚀措施.     

Comparison of the corrosion behavior of copper tubes in formic acid and acetic acid environment

Carboxylic acids with different carbon chains have different corrosion behaviors on copper tubes. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) and acetic acid (CH₃COOH) were analyzed by vapor corrosion tests, electrochemical tests, contact angle examination, optical microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The corrosion process of copper tubes in the HCOOH environment is more complex than in the CH₃COOH environment and HCOOH is easy to cause “ant nest” corrosion on copper tubes. The corrosion rate is faster and the surface of the copper tube is more easily corroded in the CH₃COOH environment due to the formation of unstable and loose corrosion products, Cu(OH)(CH₃COO)₂·2H₂O. The results of the contact angle examination showed that the contact angles of HCOOH and CH₃COOH on copper tube surface were 25° and 9°, respectively, which means that CH₃COOH is more likely to be absorbed by the surface of the copper tube evenly. Differences in the wettability of these two carboxylic acids with copper tubes are the main reason for the different corrosion phenomena. The corrosion mechanisms of copper tubes in carboxylic acid are also discussed.     

Correlation of seawater corrosion and processing of Cu-Ni alloy tubes

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