Mg含量对Al-Mg合金应力腐蚀行为的影响

采用电化学极化曲线、交流阻抗谱和慢应变速率拉伸试验结合扫描电镜观察等方法研究了不同Mg含量的Al-Mg合金的应力腐蚀开裂(SCC)行为。结果表明,随着Mg含量的增加,腐蚀电位降低,而腐蚀电流密度(i_(corr))显著增加。Al-2.5Mg合金在3种合金中表现出最低的i_(corr),与交流阻抗结果相对应。在慢拉伸试验中,Al-6.3Mg合金显示出最差的延展性,其断口形貌表现出明显的脆性断裂特征,应力腐蚀开裂敏感性最大。     

氢对Al-8％Mg合金应力腐蚀开裂的影响

铝合金中氢对应力腐蚀开裂的作用,最近以来颇为引人关注。铝合金在应力腐蚀介质中所产生的脆性以及氢脆和应力腐蚀开裂之间的密切关系在许多文献中已有所论述。然而,对氢脆和应力腐蚀开裂之间关系的详细情况并非都非常清楚了。有些作者也研究了Al—8％Mg合金的这些现象,并观察到合金有相当大的脆性,也发现它们两者有着密切的关系。本文的目的在于阐明氢对Al—8％Mg合金应力腐蚀开裂的影响,并以氢脆的观点解释应力腐蚀     

LC4铝合金的应力腐蚀研究

用Ⅱ型试样以慢拉伸方法研究了拉伸速度和极化电位对LC4铝合金应力腐蚀开裂行为的影响。采用应力腐蚀开裂面积A_(SCC)、应力腐蚀最大抗拉强度σ_(SCC)及其所对应的应变ε_(SCC)作为衡量应力腐蚀开裂敏感性的参数。结果表明,随拉伸速度降低,应力腐蚀开裂敏感性升高,但用σ_(SCC)来表现应力腐蚀开裂的敏感性不如A_(SCC)明显。阳极极化使抗拉强度下降;阴极极化时。若极化电位较小,则抗拉强度略有升高,强阴极极化抗拉强度则又会降低,说明应力腐蚀包含氢脆和阳极溶解两种机制。断口形貌观察发现,开路、阴极极化和充氢时的断口形貌相同,阳极极化则与其不同,表明开路时的应力腐蚀开裂是以氢脆为主的。     

低合金高强度抗应力腐蚀开裂海洋软管用钢的开发

通过合金成分设计,轧制、热处理工艺的探索,开发了低合金高强度海洋软管用钢,其屈服强度大于600 MPa且满足抗氢脆、抗氢致开裂、抗应力腐蚀开裂性能,并通过全浸腐蚀实验对该钢的海水腐蚀行为进行了研究。结果表明,采用低C、低Mn并复合添加耐蚀元素Cr、Mo和采用合理的热轧、冷轧、调质处理工艺,可获得满足抗应力腐蚀开裂性能的600 MPa级高强钢。耐蚀元素的添加使实验钢具有良好的耐海水腐蚀能力,腐蚀稳定状态下的平均年腐蚀速率为0.11 mm/a。     

Al—Li—Cu—Mg合金应力腐蚀性能及机理研究

利用恒应变速率方法研究了Al—Li—Cu—Mg合金的应力腐蚀开裂,包括时效条件及外加电位对应力腐蚀的影响,同时研究了试样表面相对氢浓度与外加电位及应力腐蚀时间的关系,实验结果表明,合金的应力腐蚀性能取决于时效条件,其中峰时效条件下最差,自然时效条件下最好,应力腐蚀敏感性及试样表面氢浓度与外加电位有关,阳极电位增加应力腐蚀敏感性,阴极电位低于临界电位时加速应力腐蚀,认为合金在应力腐蚀过程中阳极溶解与氢脆机制联合作用。     

温度对海洋平台用S355钢抗应力腐蚀的影响

采用慢应变速率实验(SSRT)研究了S355钢在3.5%Na Cl溶液中应力腐蚀破裂(SCC)行为,通过σ-ε曲线分析了不同温度下S355钢应力腐蚀开裂敏感性指数。采用SEM观察了断口及其孕育期、扩展区、瞬断区和腐蚀物形貌,并分析了腐蚀物化学成分。结果表明,随溶液温度升高,内积功应力腐蚀敏感性指数ISCC下降,在20~50℃范围内ISCC均小于25%,断口为韧性断口,S355钢在3.5%Na Cl溶液中没有明显的应力腐蚀倾向;随溶液温度升高,开裂源变小,而韧窝尺寸和氧化物体积变大,抗氢致开裂能力增强,说明S355钢具有较高的抗应力腐蚀性能。     

温度对Al-Zn-Mg-Cu合金应力腐蚀敏感性的影响

采用慢应变拉伸的方法研究了服役温度对石油钻杆用Al-Zn-Mg-Cu合金应力腐蚀敏感性的影响。研究表明:T6态Al-Zn-Mg-Cu合金的应力腐蚀敏感性随温度升高而升高;在20℃下的应力腐蚀敏感性要远低于40、60、80℃下的应力腐蚀敏感性;40、60、80℃下合金应力腐蚀敏感性上升幅度较小。20℃常温下应力腐蚀开裂主导机制是阳极溶解;40℃及较高温度下应力腐蚀开裂的主导机制是氢脆机制,此时阳极溶解起到辅助作用。较高的温度不仅加快了氢原子的扩散速度,而且也促进了晶界及位错的运动,使得氢脆机制起主导作用。     

Si含量对7050铝合金显微组织和抗应力腐蚀开裂的影响

分别研究Si含量为0．094％、0．134％和0．261％的3种T7651态7050铝合金的组织和应力腐蚀开裂敏感性。结果表明：随着Si含量从0．094％增加到0．261％,Mg2Si相的面积分数从0．16％增加到1．48％,并且尺寸粗化;而其它粗大相（包括Al2CuMg、Mg（Al3Cu,Zn）2和Al7Cu2Fe）的面积分数从2．42％减小到0．78％。合金的电导率随Si含量的增加而增加。合金在空气中进行慢应变速率拉伸时,抗拉强度和伸长率随Si含量的增加而降低;而在3．5％NaCl溶液中进行慢应变速率拉伸时,随Si含量增加,合金应力腐蚀开裂敏感性降低。     

Mg含量对Al-Cu-Mg合金烧结行为和力学性能的影响(英文)

采用粉末冶金方法制备Al-3Cu-Mg合金,将各合金元素的空气雾化粉末与不同含量的Mg混合,通过控制压制压力分别得到弹性变形、局部塑性变形和塑性变形的粉末样品。确定不同成分合金的烧结温度,使烧结过程中Cu的液相烧结起主导作用。采用光学显微镜和扫描电子显微镜对合金的烧结行为和断口特征进行了分析。烧结后合金的横向断裂强度随Mg含量的增加而减小,Al-3Cu-0.5Mg合金具有适中的横向断裂强度和较高的比强度。     

高温水蒸气环境中TP439不锈钢的应力腐蚀开裂敏感性

目的 研究TP439不锈钢在高温水蒸气环境中的应力腐蚀开裂行为,并探讨水蒸气和温度对其应力腐蚀开裂敏感性的影响规律。方法 采用慢应变速率拉伸试验方法研究了TP439不锈钢在400~600 ℃水蒸气环境中的应力腐蚀开裂行为,利用SEM和EDS分析试样断口区域的形貌及元素分布。结果 同一应变速率(2×10^‒5 s^‒1)下,随着温度在400~600 ℃范围内升高,TP439不锈钢在空气和水蒸气环境中的屈服强度、抗拉强度和断裂能均逐渐降低,延伸率逐渐增大。400 ℃和500 ℃时,试样在水蒸气环境中的抗拉强度较空气环境中有所降低,而延伸率较空气环境中增大。600 ℃时试样在水蒸气环境中的力学性能较空气环境中无明显差别。试样在400、500、600 ℃水蒸气环境中的应力腐蚀开裂敏感性指数分别为0.7%、1.2%和‒2.8%,应力腐蚀开裂敏感性较低。试样在400~600 ℃水蒸气环境中的断口均呈现韧性断裂特征,断口形貌整体由韧窝和微孔组成,颈缩现象显著,断口附近未发现二次裂纹。温度在400~600 ℃范围内升高时,断口的韧窝特征更加明显,颈缩程度逐渐增大,600 ℃时断口侧面的氧化膜表面Cr含量明显降低,主要由Fe的氧化物形成。结论 水蒸气对TP439不锈钢的应力腐蚀开裂行为起促进作用。基于应力腐蚀开裂敏感性指数和断口的分析,在应变速率为2×10^‒5 s^‒1的400~600 ℃水蒸气环境中,TP439不锈钢的应力腐蚀开裂敏感性较低。     

Comparison of microstructure and corrosion properties of Al-Zn-Mg-Cu alloys 7150 and 7010

The influence of coarse Cu-bearing particles, matrix and subgrain boundary precipitates on the stress corrosion susceptibility of the Al-Zn-Mg-Cu alloys was investigated. The strength of 7150 alloy is about 15 MPa higher than that of 7010 alloy. The 7010 alloy exhibits higher resistance to stress corrosion cracking as compared with the 7150 alloy. The coarse Cu-bearing particles are detrimental to the resistance to stress corrosion cracking. The increase of size of matrix and subgrain boundary precipitates decreases the susceptibility of stress corrosion. The anodic dissolution and hydrogen embrittlement govern the cracking process. The severity of stress corrosion cracking is shown to be related to the coarse Cu-bearing particles, matrix and subgrain precipitates in Al-Zn-Mg-Cu alloys.     

Effect of high-temperature pre-precipitation on mechanical properties and stress corrosion cracking of Al-Zn-Mg alloys

1　INTRODUCTIONMediumandhighstrengthAl Zn Mgseriesaluminumalloysarethe primaryweldingstructurematerialsofaerocrafts ,transportationvehiclesandmilitaryequipments[1,2 ] ,duetoitsbetterweldabilityandexcellenttechnologicalproperty .Buttheexten siveutilizationofthesealloysishamperedbyitspoorstresscorrosioncracking (SCC)resistance[3,4 ] .Ac cordingly ,manystudieshavebeenconcernedwithsuchaproblemashowtoimprovestresscorrosionre sistanceofAl Zn Mgalloyswithnon deterioratedstrength[3,58] .Atpres…     

Al-Zn-Mg-Cu系铝合金中不同区域电子结构及应力腐蚀机理分析

利用计算机编程建立了Al--Zn--Mg--Cu合金 (7175铝合金) 中α--Al, η相及α--Al大角度晶界原子集团模型, 采用递归法计算 合金中Zn, Mg, Cu和H的环境敏感镶嵌能、原子间相互作用能、Fermi能级和态密度等电子结构参数, 分析了合金的应力腐蚀机理. 计算 结果表明: Mg, Cu和H容易在晶界偏析. Mg对H具有吸引作用, 促进H在晶界偏析, 引起晶界氢脆; Zn增大晶界与晶内的电位差, 降低合 金抗腐蚀性; Cu能减小晶界与晶内Fermi能级差, 降低晶界与晶内的电位差, 具有减缓合金腐蚀的作用. 计算结果还表明: η相的Fermi能 级最高, 腐蚀过程中作为阳极优先溶解. 由于η相俘获H, 当晶界析出断续η相时可减弱晶界H的偏析, 提高抗腐蚀性; 但晶界连续分布η相则形成腐蚀通道, 加速腐蚀进程.     

Correlations among stress corrosion cracking,grain-boundary microchemistry,and Zn content in high Zn-containing Al–Zn–Mg–Cu alloys

The correlations among the corrosion behaviour, grain-boundary microchemistry, and Zn content in Al–Zn–Mg–Cu alloys were studied using stress corrosion cracking (SCC) and intergranular corrosion (IGC) tests, combined with scanning electron microscopy (SEM) and high-angle angular dark field scanning transmission electron microscopy (HAADF-STEM) microstructural examinations. The results showed that the tensile strength enhancement of high Zn-containing Al–Zn–Mg–Cu alloys was mainly attributed to the high density nano-scale matrix precipitates. The SCC plateau velocity for the alloy with 11.0 wt.% Zn was about an order of magnitude greater than that of the alloy with 7.9 wt.% Zn, which was mainly associated with Zn enrichment in grain boundary precipitates and wide precipitates-free zones. The SCC mechanisms of different Zn-containing alloys were discussed based on fracture features, grain-boundary microchemistry, and electrochemical properties.     

Modellversuch zum Mechanismus der Spannungsrißkorrosion von AlZnMg-Legierungen

Model experiments concerning the mechanism of stress corrosion cracking of AlZnMg alloys For the experimental clarification of scc of AlZnMg alloys, tubes were inside filled with the corrosive medium and subjected to tensile stresses. In order to increase localised tension, circumferencial notches were made. The formation of sccfracture on the outside of the tubes can only be explained by hydrogen embrittlement. The equilibrium solubility of the grain boundary for hydrogen is dependent upon the value of the effective normal tensile stress. The grain boundary adhesive strength is reduced to the diffused hydrogen producing a decohesive effect. This results in intercrystalline brittle fracture in the range of the elastic tension.     

Hydrogen effects during IGSCC of pure Al-5Mg alloy in NaCl media

The conditions to propagate an intergranular stress corrosion crack in pure, precipitate-free, Al-5Mg alloy in 30 g/l NaCl have been determined. SCC tests are performed on specimens with a thin notch which favours single cracking and solution confinement. Slow strain rate tests in a simulated confined medium without oxygen are used to simulate the natural confinement. They show that the main cathodic reaction during SCC is the reduction of hydrogen. Reversible grain boundary embrittlement is obtained by localised hydrogen pre-charging. The role of hydrogen during intergranular stress corrosion cracking is therefore established, in close relation with localised dissolution.     

A comparison of hydrogen embrittlement susceptibility of two austenitic stainless steel welds

Slow displacement rate tensile tests were carried out to assess the effect of hydrogen embrittlement on notched tensile strength (NTS) and fracture characteristics of AISI 316L and 254 SMO stainless steel (SS) plates and welds. 254 SMO generally exhibited a better resistance to hydrogen embrittlement than 316L. The strain-induced transformation of austenite to martensite in the 316L SS was responsible for the high hydrogen embrittlement susceptibility of the alloy and weld. Sensitized 254 SMO (i.e., heat-treated at 1000 °C/40 min) base plate and weld comprised of dense precipitates along grain boundaries. Interfacial separation along solidified boundaries was observed with the tensile fracture of 254 SMO weld, especially the sensitized one. Dense grain boundary precipitates not only reduced the ductility but also raised the susceptibility to sulfide stress corrosion cracking of the sensitized 254 SMO plate and weld.     

Stress-corrosion cracking of aged AlCuMg alloys in NaCl solution

Pitting potentials and stress corrosion life-times of AlCuMg alloys (mainly 2024 alloy) with various ageing structures have been measured in a de-aerated 1M NaCl solution under conditions of controlled potential. The aged alloy, which has the higher susceptibility to stress-corrosion cracking, showed two pitting potentials corresponding to pitting at the grain boundaries and within the grains. The susceptibility of the alloys to intergranular stress-corrosion cracking occurred at potentials above the pitting potential of the grain boundaries. The intergranular stress-corrosion cracking is caused not by the dissolution of the grain boundary precipitates (S phase) but by the pitting dissolution of the solute-denuded zones along the grain boundaries. Aspects of SCC in the alloys are similar to those in the Al-4%Cu alloy without Mg.     

Interkristalline,Kornflächen- und Spannungsriß-Korrosion von ausgehärteten AlZnMg 1-Legierungen

Intercrystalline corrosion, grain-phase corrosion and stress-corrosion cracking of aged AlZnMg1 alloys Potentiostatic polarisation curves and stress corrosion crack propagation of a pure and a commercial AlZnMg1-alloy, both peakhardened either by warm or by double ageing, were investigated in airsaturated sodium halide and sulfate solutions at a temperature of 303 K. For this, propagation of crack tips was observed microphotographically under potentiostatic conditions and under constant stress using specimens precracked by fatique corrosion. The pure alloy contents (weight percent): Zn 4,4; Mg 1,26; Fe 0,05; Si 0,006; balance Al, the commercial alloy: Zn 5,05; Mg 1,2; Fe 0,23; Si 0,1; Mn 0,23; Cr 0,2; Cr 0,2; Ti 0,074; Zr 0,12; Cu 0,056; balance Al. In sodium halide solutions either grain boundary and grain attack or only grain attack occurs at a potential region more positive than the respective breakdown potential. At the more negative restpotential no attack can be observed. The influence of concentration of chloride ions on the velocity of discontinuous crack propagation in the pure alloy, which starts without any initiation stage, is different for both heat treatments. No crack propagation is observed in the commercial alloy and in any case in sulfate solutions. The obtained stress corrosion cracking results may be explained by hydrogen embrittlement of the area around the crack tip.     

晶界结构在不同热处理下对铝镁合金腐蚀规律的研究现状

铝镁合金是未来应用汽车领域发展具有很大潜力的一类重要材料.通常,在商品中的铝镁合金,镁的质量分数在0.5%～13%.汽车制造商通常选用镁的质量分数在4.5%以上,然而研究发现,当镁的质量分数超过3%的时候,会引起晶界间腐蚀,从而造成应力腐蚀开裂.此现象未见文献对其进行系统的分析和研究.本文主要介绍铝镁合金在不同的热处理...