添加RE和Ti元素对Zn-2.5Al-3Mg合金微观结构和耐腐蚀性能的影响

采用XRD、SEM、TEM和XPS等研究了RE和Ti元素对Zn-2.5Al-3Mg合金微观结构和耐蚀性的影响。结果表明,Zn-2.5Al-3Mg合金的微观结构由富Zn相、二元共晶（Zn-MgZn₂/Mg₂Zn₁₁）和三元共晶（Zn/Al/Mg₂Zn₁₁）组成,而含有RE和Ti元素的合金中出现了新相(Ce_1-xLa_x)Zn₁₁和Al₂Ti。电化学阻抗谱表明,相对于Zn-2.5Al-3Mg合金,Zn-2.5Al-3Mg-0.1RE-0.2Ti合金的耐蚀性得到了显著的提高。XPS分析结果表明,RE元素的添加促进腐蚀产物Zn₅(CO₃)₂(OH)₆和MgAl₂O₄的形成,而RE和Ti元素的同时添加促进腐蚀产物 Zn₅(CO₃)₂(OH)₆、ZnAl₂O₄和MgAl₂O₄的形成,且都抑制了疏松多孔ZnO的生成。Zn₅(CO₃)₂(OH)₆、ZnAl₂O₄和MgAl₂O₄能够很好地粘附在试样表面,提供一层致密的保护层,从而提高Zn-2.5Al-3Mg合金的耐腐蚀性。     

Surface characterization of passive film formed on nitrogen ion implanted Ti-6Al-4V and Ti-6Al-7Nb alloys using SIMS

The aim of this paper is to study the effect of N⁺ ion implantation on corrosion and phase formation on the implanted surfaces of Ti-6Al-4V and Ti-6Al-7Nb alloys. Nitrogen ion was implanted on Ti-6Al-4V and Ti-6Al-7Nb alloys at an energy of 70 and 100 keV, respectively using a 150 keV accelerator at different doses ranging from 5 × 10¹⁵ to 2.5 × 10¹⁷ ions/cm². Electrochemical studies have been carried out in Ringer’s solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The implanted surfaces of such modified doses were electrochemically passivated at 1.0 V for an hour. Secondary ion mass spectroscopy was used to study and characterize titanium oxide and titanium nitride layers produced on implanted surface and to correlate them with the corrosion resistance. The nature of the passive film of the implanted-passivated specimen was compared with the unimplanted-passivated as well as as-implanted specimens.     

Correlation of stress corrosion cracking behaviour with electrical conductivity and open circuit potential in Al‐Li‐Cu‐Mg‐Zr alloys

Studies of stress corrosion cracking (SCC) behaviour by slow strain rate test (SSRT), potentiodynamic electrochemical polarization and measurement of electrical resistivity were carried out on 8090 and 1441 Al‐Li‐Cu‐Mg‐Zr alloys in their peak aged T8, over aged T7 and retrogressed and reaged (RRA) T77 tempers. It has been found that the SCC resistance is maximum in the T7 temper, least in the T8 temper and in the RRA T77 tempers it lies in between to that of the T8 and T7 tempers, indicating that RRA heat treatment given to the T8 temper of both alloys caused an improvement of SCC resistance. Further, studies on the electrical conductivity measurements and electrochemical polarization of all tempers of both alloys showed that T7 temper has maximum electrical conductivity and most negative (anodic) open circuit potential (OCP), T8 has the minimum and the least respectively, whereas, in the T77 tempers these values lie in between to those of the T8 and T7 tempers. Therefore, a definite pattern of variation of these results with RRA treatment draws an attention to correlate SCC behaviour, electrical conductivity and OCP values which are explained on the basis of microstructural features revealed by TEM and XRD studies.     

油气开采用钛合金石油管材料耐腐蚀性能研究

选取5种油气开发常用钛合金材料(Ti-6Al-4V、Ti-6Al-4V-0.1Ru、Ti-6Al-2Sn-4Zr-6Mo、Ti-3Al-8V-6Cr-4Zr-4Mo和Ti-5.5Al-4.5V-2Zr-1Mo)为研究对象,使用高温高压釜模拟国内典型严酷服役工况环境,研究了不同钛合金材料耐均匀腐蚀、局部腐蚀、点蚀、应力腐蚀开裂(SCC)及缝隙腐蚀的性能,通过使用扫描电镜和能谱分析等手段对腐蚀形貌和腐蚀产物进行了分析,并使用电化学方法对不同合金的耐腐蚀机理进行了研究。结果显示,在所测试工况条件下,所有钛合金材料腐蚀反应均为阳极控制过程,均匀腐蚀速率均低于0.001mm/a,并且对应力腐蚀开裂均有良好的抗力。Ti-6Al-4V和Ti-5.5Al-4.5V-2Zr-1Mo合金出现明显的点蚀和缝隙腐蚀问题。对腐蚀机理研究表明,在工况条件温度下,随着pH值的降低,所有钛合金均发生自腐蚀电位降低,极化电阻减小,腐蚀电流增大,耐腐蚀性能下降,其中Ti-6Al-4V耐腐蚀性能下降的最为明显,研究结果为油气开发工况下钛合金石油管的选材和缝隙腐蚀问题防治提供理论基础。     

Synergistic abrasive—corrosive wear of chromium containing steels

Abstract

Commercial and experimental steels containing various chromium concentrations have been assessedfor their resistance to the combined effects of abrasion and corrosion. The degree of work hardening and macro- and microtoughness of low carbon martensite alloys, dual phase alloys, and metastable austenitic alloys provide good abrasion resistance, while chromium contents > 8% are required. Abrasion and corrosion are synergistic since the kinetics of corrosion are influenced by abrasion. The effects of the frequency of abrasion and corrosion are different for steels of different chromium contents. Low chromium steels perform better under lowfrequency conditions, whereas steels with higher chromium contents resist wear better when there are frequent abrasive periods.     

Enhancing Biocompatibility and Corrosion Resistance of Ti-6Al-4V Alloy by Surface Modification Route

Titanium (Ti) and its alloys are widely used as candidate materials for biomedical implants. Despite their good biocompatibility and corrosion resistance, these materials suffer from corrosion after implantation in biological environments. The aim of this research work is to study the effect of two coatings on biocompatibility and corrosion behavior of Ti-6Al-4V biomedical implant material. Hydroxyapatite (HA) and hydroxyapatite/titanium dioxide (HA/TiO₂) coatings were thermal-sprayed on Ti-6Al-4V substrates. In the latter case, TiO₂ was used as a bond coat between the substrate and HA top coat. The corrosion behavior of coated and un-coated samples in Ringer’s solution was studied by potentiodynamic and linear polarization techniques. Before and after corrosion testing, XRD and SEM/EDS techniques were used for the analysis of phases formed and to investigate microstructure/compositional changes in the coated specimens. The cellular response was analyzed by the MTT (microculture tetrazolium) assay. The results showed that both the HA, as well as, the HA/TiO₂ coatings significantly increased the corrosion resistance of the substrate material. The HA coating was found to be more biocompatible as compared to the un-coated and HA/TiO₂-coated Ti-6Al-4V alloy.     

Investigations on role of HVOF sprayed Co and Ni based coatings to combat hot corrosion

Abstract

This paper aims to investigate the hot corrosion resistance of high velocity oxy-fuel (HVOF) sprayed cobalt based (Stellite-6) and nickel based (Ni–20Cr) coatings deposited on the superalloy Superni-718 (Ni–19Cr–18˙5Fe–5˙13Ta–3˙05Mo–0˙9Ti–0˙5AI–0˙18Mn–0˙18Si–0˙15Cu–0˙04C) in the Na₂SO₄–60%V₂O₅ salt environment at 900°C under cyclic conditions. The X-ray diffractometry, scanning electron microscopy/energy dispersive analysis and electron probe microanalyser techniques were used to study the corrosion products with respect to their morphology, phase composition and element concentration. The thermogravimetric technique was used to establish the kinetics of corrosion. The bare alloy underwent severe hot corrosion attack. The Ni–20Cr coating shows excellent hot corrosion resistance with negligible spallation, whereas Stellite-6 coating reveals less hot corrosion resistance and more spallation. The hot corrosion resistance of Ni–20Cr coating has been attributed to the formation of oxides of chromium, nickel and spinel of nickel chromium. The oxides of silicon, chromium, cobalt and spinels of cobalt–chromium and nickel–chromium have contributed for hot corrosion resistance of Stellite-6 coatings.     

High temperature Corrosion behaviour of iron aluminides and iron-aluminium-chromium alloys

The high temperature corrosion of different iron aluminides and iron-aluminium-chromium alloys containing between 6 and 17 wt% aluminium, 2 and 10 wt% chromium and additions of mischmetal has been investigated in air as well as in carburising, chlorinating and sulphidising environments. It was found that all alloys showed excellent corrosion resistance to both oxidation in air and carburisation in CH₄/H₂ up to at least 1100°C and to sulphidation in SO₂/air up to at least 850°C. In these environments the corrosion behaviour is not influenced by the concentrations of aluminium and chromium. In oxygen deficient H₂S-atmospheres, however, the corrosion behaviour depends sensitively on the aluminium and chromium concentration. At least 12 wt% aluminium in chromium-free alloys or 10 wt% aluminium in alloys containing 10 wt% chromium are required to provide sulphidation resistance at 550°C. The chlorination resistance of iron-aluminium-chromium alloys is low due to their formation of volatile aluminium chlorides.     

Mg和Cu在Al-Zn-Mg合金时效初期的Monte Carlo模拟

采用Monte Carlo方法模拟研究Al-6Zn-(2Mg)和Al-10Zn-1.9Mg-(1.7Cu)合金时效初期微观结构的演变过程,并分析Mg和Cu的基本作用。结果表明:时效初期,Al-6Zn合金中的Zn原子有较强的团聚倾向,形成了明显的Zn原子簇;而在Al-6Zn-2Mg合金中出现明显的Zn原子簇、Zn-Mg原子簇及少量的Mg原子簇。Mg的作用是通过Mg和Zn原子间强烈的相互作用形成Zn、Mg原子交替排布的短程有序结构。含铜的Al-10Zn-1.9Mg-1.7Cu合金中,不仅形成了Zn原子簇、Mg原子簇和Zn-Mg原子簇,还形成了少量Zn-Cu原子簇、Mg-Cu原子簇和Zn-Mg-Cu原子簇。Cu的存在促进Zn原子和Zn-Mg原子团簇化,但对Mg原子的团簇化影响不大。     

含Al2Ca相和Mg2Ca相Mg-Al-Ca-Mn合金经等通道转角挤压加工后的腐蚀性能(英文)

为了研究Al₂Ca相和Mg₂Ca相对Mg-Al-Ca-Mn合金腐蚀行为的影响,采用金相显微镜、扫描电子显微镜、浸泡和电化学测试对仅含Al₂Ca相(2Ca)和仅含Mg₂Ca相(4Ca)的铸态及ECAP态合金进行研究。在腐蚀初期,两种铸态合金的腐蚀速度比ECAP合金的慢。随着腐蚀时间的延长,ECAP合金的腐蚀程度变得比铸态合金轻微,这主要归因于ECAP合金中第二相的有效细化及分散。此外,2Ca合金的腐蚀程度始终小于4Ca合金,表明Al₂Ca相比Mg₂Ca相更有利于提高Mg-Al-Ca-Mn合金的耐腐蚀性能。最后,根据合金腐蚀表面的形貌观察和电化学测试结果,对由Al₂Ca相和Mg₂Ca相的分布和形貌引起合金的不同腐蚀机理进行讨论。     

Corrosion resistance of Mg–8·8Li alloy compared with AZ91

Abstract

The superlight Mg–Li alloys exhibit good formability but poor corrosion resistance due to the alloying of lithium. In this paper, the corrosion behaviour of Mg–8·8Li alloy was investigated by electrochemical measurements, corrosion morphology observations and weight loss determination. The results indicate that Mg–8·8Li alloy displays worse corrosion resistance than AZ91D alloy in the early stages of corrosion. However, the corrosion resistance of AZ91D alloy declines and becomes worse than Mg–8·8Li alloy with increasing exposure time. In addition, it is found that a 250°C annealing treatment has a detrimental effect on the corrosion resistance of Mg–8·8Li alloy.     

微量Zr、Er对Al-Zn-Mg合金组织与性能的影响

采用硬度、拉伸性能、电阻率和抗应力腐蚀性能测试及金相组织观察等方法,研究了微量Zr、Er对Al-4.4Zn-2.4Mg(质量分数,下同)合金组织与性能的影响.结果表明,单独添加Zr的细晶作用优于单独添加Er以及Er、Zr复合添加,Er、Zr复合添加能显著抑制合金的再结晶行为,Er、Zr复合添加后合金的力学性能和单独添加微量Zr的基本相当,但Er、Zr复合添加后合金抗应力腐蚀性能优于单独添加微量Er、Zr,Er、Zr复合添加的Al-Zn-Mg合金综合性能最好.Er、Zr复合添加提高应力腐蚀抗力是通过抑制再结晶获得纤维组织间接实现的.     

The influence of Mg addition and hydrostatic extrusion HE on the repassivation ability of pure Al,AlMg1 and AlMg3 model alloys in 3.5 wt-% NaCl

ABSTRACT

Commercially pure aluminium and two model aluminium–magnesium alloys were subjected to hydrostatic extrusion (HE). The microstructure of materials was observed using optical microscopy (OM). All materials were subjected to electrochemical corrosion tests in the 3.5?wt-% water solution of sodium chloride. The potentiodynamic polarisation measurements and electrochemical impedance spectroscopy were performed after samples’ immersion in open circuit potential. The surface of samples after corrosion examination was observed with the use of scanning electron microscopy. It was stated that all undeformed materials underwent pitting corrosion and further pits repassivation, while after HE pitting was also observed, but pit repassivation did not occur. This may be related to the microstructural changes caused by deformation, such as grain refinement. What is more, the pits character changed with the addition of a different amount of Mg to Al. Deterioration of corrosion resistance was also observed for all materials after HE.     

Effect of thermal exposure on the microstructure,tensile properties and the corrosion behaviour of 6061 aluminium alloy sheet

Sheet material of the Al‐Mg‐Si alloy 6061 in the tempers T4 and T6 was thermally exposed at temperatures ranging from 85 to 120°C for 1000 h. The microstructure, tensile properties and the corrosion behaviour in the different heat treatment conditions were investigated using differential scanning calorimetry and transmission electron microscopy as well as performing tensile tests and various corrosion tests. The additional heat treatments, which should simulate aging during long‐term service usage, caused an increase in strength of 6061‐T4 sheet, associated with changes in the naturally aged microstructure. Thermal exposure at 120°C for 1000 h resulted in tensile and corrosion properties being similar to those obtained for peak‐aged sheet. Alloy 6061 in the T6 temper exhibited microstructural stability when additionally heat treated at 85 and 120°C for 1000 h. No significant alterations in the microstructure, tensile properties, and corrosion performance were observed after exposure to slightly elevated temperatures.     

Effects of Al content on the corrosion properties of Mg–4Y–xAl alloys

The corrosion performances of Mg–4Y–xAl (x = 1, 2, 3, and 4 wt%) alloys in the 3.5% NaCl electrolyte solution are investigated by electrochemical tests, weight loss measurement and corrosion morphology observation. The results indicate that corrosion modes for the alloys are localized corrosion and the filiform type of attack. With Al concentration increasing from 1 to 4 wt%, the corrosion rate of Mg–4Y–xAl alloys decreases firstly and then increases, and WA42 alloy shows the best corrosion resistance. The addition of Al element to Mg–4Y alloys leads to the formation of Al₂Y and Al₁₁Y₃ intermetallic compounds and reduces the proportion of Mg₂₄Y₅ phase. Corrosion resistance of the Mg–4Y–xAl alloys mainly depends on the size and distribution of the second phases. Besides, the addition of excessive Al can greatly consumes the Y element in the matrix, thus leading to a less protective film on the alloys. The effect of the relative Volta potential changes between the second phases and α-Mg on corrosion resistance of Mg–4Y–xAl alloys is insignificant. The main corrosion products of the Mg–4Y–xAl alloys are Mg(OH)₂, Mg₃(OH)₅Cl·4H₂O, Mg_0.72Al_0.28(CO₃)_0.15(OH)_1.98(H₂O)_0.48, and Mg₄Al₂(OH)₁₂CO₃·3H₂O.     

用球差校正扫描透射电镜研究人工时效7075铝合金的耐蚀性（英文）

使用先进的球差校正扫描透射电子显微镜研究人工时效7075铝合金耐腐蚀性增强机制。通过阻抗谱、等效电路分析、极化测量和浸泡试验,研究人工时效7075铝合金在3.5%(质量分数) NaCl溶液中的腐蚀行为。结果表明,人工时效时间越长,7075铝合金的耐腐蚀性越好。这可能归因于扫描透射电镜技术揭示的以下显微组织特征：在过时效条件下,晶界处的铜偏析有助于延缓晶间腐蚀,在Al₁₈Mg₃(Cr,Mn)₂分散体表面形成的Mg(Zn,Cu)₂沉淀有效地将作为腐蚀阴极的分散体与铝基体隔离。这项研究证明,可以通过适当的合金化和人工时效来设计耐腐蚀合金的可能性。     

Mg量对过共晶Al-18%Si合金组织与性能的影响

为改善Al-18％Si组织形貌,利用扫描电镜与金相显微镜观察了不同含Mg量过共晶Al-Mg-18％Si合金的显微组织,并测试相应的力学性能,研究了强化处理的作用。结果表明:镁在过共晶Al-Si合金中的作用是通过热处理来实现,随镁含量的增加,合金的强度稍有增加,但伸长率有所下降。为了提高金相组织与力学性能,Mg量应控制在0．5％-3．0％。     

High temperature interaction of Al/Si-modified Fe-Cr alloys with KCl

The corrosion behaviour of pure iron, pure chromium, and aluminium/silicon alloyed Fe-Cr materials was investigated at 650 °C in air accompanied by gaseous or solid KCl salt. The corrosion rates of these materials with KCl salt are high and they are strongly affected by the salt amount, the types of the alloying elements and the concentration of chromium. The dominant degradation mechanism for the chromia-forming alloys by KCl attack is the preferential formation of potassium chromate over the conventionally protective chromia, characterized by typical features of bubbles, cracks, volatility and severe spallation for the corrosion products. A detrimental effect of chromium is confirmed. Al-alloying addition to Fe-Cr alloys is beneficial by enhancing the corrosion resistance. Silicon is more effective in promoting the corrosion resistance of Fe-Cr alloys by forming a stable and dense oxide layer in the inner zone which suppresses the rapid growth of iron oxides.     

铝合金在海洋环境中的腐蚀研究(Ⅱ)--海水全浸区16年暴露试验总结

总结了铝合金在青岛海域海水全浸区暴露16年的腐蚀结果，防锈铝LF2Y2，LF6M（BL），F21M，180YS在海水全浸区有好的耐蚀性，工业纯铝L4M，锻铝LD2CS的耐蚀性较差，无包铝层的硬铝LY12CZ和超硬铝LC4CS在海水中的耐蚀性很差，硬铝，超硬铝的包铝层起牺牲阳极作用，使基体受到保护，海生物污损对铝合金在海水中的腐蚀有明显影响，镁、锰能提高铝的耐海水腐蚀性，硅明显降低铝的耐蚀性，铜严重损害铝的耐蚀性，腐蚀电位较负的铝合金耐海水腐蚀性较好，腐蚀电位较正的铝合金耐海水腐蚀性较差。     

Exfoliation corrosion of 7150 Al alloy with various tempers and its electrochemical impedance spectroscopy in EXCO solution

The exfoliation corrosion susceptibility and electrochemical impedance spectroscopy (EIS) of 7150 Al alloys with T6, T73, and RRA (retrogression at 175 °C for 3 h) tempers in EXCO solution were investigated. The anodic equilibrium precipitate η(MgZn₂) is continuous or closely spaced at the grain boundaries in the 7150‐T6 Al alloy, resulting in its greatest susceptibility to exfoliation corrosion. The grain boundary η precipitates in the RRA and T73 treated 7150 Al alloys are coarsened and show a clear discontinuous nature; they possess similar exfoliation corrosion sensitivity and their exfoliation corrosion resistance is greatly increased. At the beginning of immersion in EXCO solution, the EIS plot of the 7150 Al alloys is composed of a capacitive arc in the high to medium frequency range and an inductive component in the medium to low frequency range. As immersion time is increased, exfoliation corrosion with different corrosion ratings occurs on the surface of the 7150 Al alloy with various tempers, two capacitive arcs appear in the high to medium and medium to low frequency ranges, respectively. The fitted medium to low frequency capacitance C₂ of 7150‐T6 Al alloy, corresponding to the new surface caused by the exfoliation corrosion, is much greater than that of the T73 and RRA treated 7150 Al alloy, which is consistent with the greatest exfoliation corrosion susceptibility of the 7150‐T6 Al alloy.