夯实钢管混凝土桩环境中X60管线钢的腐蚀行为研究

研究了X60管线钢在含水土壤和NS4溶液中的应力腐蚀行为。结果表明,在含水土壤中,当应变速率小于或者等于0.67×10~(-7)s~(-1)时,管线钢的应力腐蚀敏感性分别为27.9和25.7;在NS4溶液中,应变速率大于或者等于1.33×10~(-5)s~(-1)时不会发生应力腐蚀。恒载荷应力腐蚀断口形貌与慢应变应力腐蚀断口形貌类似,都具有准解理区和细小二次裂纹形态。     

夯实钢管混凝土桩环境中X60管线钢的腐蚀行为研究

研究了X60管线钢在含水土壤和NS4溶液中的应力腐蚀行为。结果表明,在含水土壤中,当应变速率小于或者等于0.67×10~(-7)s~(-1)时,管线钢的应力腐蚀敏感性分别为27.9和25.7;在NS4溶液中,应变速率大于或者等于1.33×10~(-5)s~(-1)时不会发生应力腐蚀。恒载荷应力腐蚀断口形貌与慢应变应力腐蚀断口形貌类似,都具有准解理区和细小二次裂纹形态。     

ZGOCr13Ni4Mo不锈钢在高温高压水中的应力腐蚀性能研究

本文采用恒应变速率法,研究了核电站一回路水质对ZG0Crl3Ni4Mo不锈钢应力腐蚀开裂性能的影响。试验结果表明,该不锈钢在上述介质中具有一定的应力腐蚀敏感性,但不严重;在慢应变速率拉伸条件下,该钢的应力腐蚀敏感系数为93.9％。     

5083铝合金气胀成形恒应变速率压力加载方式研究

采用国产工业态5083铝合金,通过气胀成形方式试制高铁车窗零件。对5083铝合金原始金相组织进行分析,发现其平均晶粒尺寸为24μm,远大于国外细晶材料的晶粒尺寸,很难进行超塑成形,因此选择合适的成形参数(成形温度、应变速率、压力加载曲线)来弥补材料在超塑性能上的不足。在不同温度和应变速率条件下对试样进行高温拉伸试验,结果表明:当温度小于475℃,伸长率普遍小于100%;当温度为550℃时,伸长率受应变速率影响变化剧烈,不适合作为成形温度。因此选择气胀成形的温度为525℃,应变速率为6. 56×10~(-4)s~(-1)。通过对成形过程中圆角的应力应变状态进行分析,得到了圆角成形的恒应变速率压力加载方式,并研究了当圆角两边夹角角度变化时恒应变速率压力加载曲线的差别。     

核电站不锈钢焊接接头的应力腐蚀行为

采用恒载荷应力腐蚀试验、恒变形应力腐蚀试验、慢应变速率试验等研究了S30403、S32101和S32205不锈钢焊接接头在硼酸溶液中的应力腐蚀行为。结果表明：经720 h的恒载荷、恒变形应力腐蚀试验后,3种不锈钢焊接接头均未发生断裂;在慢应变速率试验中,3种不锈钢接接头耐应力腐蚀性能的优劣顺序为S32205>S32101>S30403; Cl^-含量提高、pH降低、温度升高、氧含量提高均会使得不锈钢焊接接头的应力腐蚀敏感性升高,其中介质pH的影响比其他三种因素的影响都更加显著。     

5083铝合金最佳超塑性变形行为

采用最大m值法研究5083铝合金不同轧制方向的超塑性。在500℃～535℃温度范围内,得到其试样延伸率以及最佳变形温度为525℃,同时对比恒速度法、恒应变速率法在525℃的超塑性能。实验结果表明,5083铝合金轧制后,晶粒产生各向异性,导致不同轧制方向的延伸率有显著差异。在温度500℃、525℃和535℃下采用最大m值法拉伸,其纵向试样延伸率分别为264%、331%、317%,而横向试样延伸率则分别为98%、129%、119%,纵向试样延伸率显著大于横向试样延伸率。在温度525℃下,5083铝合金基于最大m值法的拉伸效果最好,其纵向试样最大延伸率为331%,拉伸时间为3846s;在相同温度下,用恒速度法、恒应变速率法拉伸,其纵向试样最大延伸率分别为316%、302%,而拉伸时间分别为9141s、12602s,最大m值法的延伸率略大于恒速度法、恒应变速率法的延伸率,但最大m值法的拉伸时间较恒速度法和恒应变速率法有大幅缩减。     

基于最大m值法的超塑性胀形最佳压力加载方式

采用最大m值法拉伸试验获得了随应变变化的最佳应变速率关系曲线,以控制钣金超塑胀形气压加载,使得板料变形集中部位的实际等效应变速率等于变化的最佳应变速率,而非等于恒应变速率拉伸获得的最佳应变速率定值,从而获得比目前基于恒应变速率超塑胀性更优良的成形性能。以2A12铝合金为研究对象,采用最大m值法拉伸实验获得其最佳应变速率关系曲线,以控制超塑性胀形,并与恒应变速率胀形进行比较;为改善壁厚均匀性,设计了正反胀形模具与工艺,并结合有限元软件MSC.Marc 2010,对整流罩进行单向和正反向胀形模拟,并进行实验验证。结果表明,对于单向胀形,基于最大m值法的简化应变速率胀形,其成形时间仅为760s,较恒应变速率胀形3 360s大幅缩短,而二者的减薄率分别为70.4%和70.9%,在降低减薄率的同时,极大的提高了胀形效率;基于最大m值法的简化应变速率正反胀形,零件最小壁厚为1.157mm,较基于最大m值法的简化应变速率单向胀形零件的最小壁厚0.887mm有一定程度增加,而不均匀性则由69.97%降为28.9%,有效改善了壁厚均匀性;实验证明,采用最大m值法的胀形件的最小壁厚有所提高,均匀性得到了有效改善,且壁厚分布与模拟结果相吻合。     

水质稳定剂Rp-04L对304不锈钢在高硬度循环冷却水中应力腐蚀行为的影响

采用慢应变速率法和恒应变原位电化学测试法研究了水质稳定剂Rp-04L对304不锈钢在高硬循环冷却水中应力腐蚀行为的影响.结果表明:水质稳定剂Rp-04L对304不锈钢在高硬度循环冷却水中的应力腐蚀破裂有明显的抑制作用.当在冷却水中加入100 mg/L的Rp-04L时,304不锈钢的应力腐蚀敏感性明显降低.     

Ti-1023合金超塑性压缩时的流动应力及显微组织

在α＋β两相区和β单相区对Ti-1023合金进行了恒应变速率等温超塑性压缩试验,实测得到了一组流动应力-应变曲线。实验结果表明：应变速率对Ti-1023合金的流动应力有显著影响,变形温度对流动应力的影响程度与应变速率大小密切相关;较低温度快速压缩时易得到均匀细小的等轴α相组织,慢速压缩时组织有一定粗化。较佳超塑性压缩温度为760℃～740℃,应变速率可根据锻件成形、组织性能及生产率的需要在一定范围内选取。     

MP159合金热加工工艺参数研究

通过对Ｔｈｅｒｍｅｃｍａｓｔｅｒ－Ｚ型热加工模拟试验机上等温恒应变速率压缩试验结果分析，首次提出了钴基高温合金ＭＰ１５９的热加工工艺参数范围。     

Mechanistic study of stress corrosion cracking of carbon steel in ethanol

Mechanistic study of stress corrosion cracking of carbon steel in fuel‐grade ethanol was made using slow strain rate testing and constant tensile load testing at yield strength stress level of the steels. Characterization of the fracture surface was made using SEM and SEM–EDS. Selective dissolution of ferrite from pearlite phase was observed. Crack initiation took place preferably from pearlite phase. Corroded zones consisting of crystallographic pits were found from fracture surfaces.     

High-temperature high-pressure SCC testing of corrosion-resistant alloys

Stress corrosion cracking test methods of corrosion-resistant alloys are reviewed. The interest to write a review on this topic was drawn by demands for oil country tubular goods applicable in deep wells with high pressures, high temperatures, and the presence of H₂S, where stress corrosion cracking is one of the most critical failure modes. All conventional methods for determining the stress corrosion cracking resistance of an alloy, mainly slow strain rate testing, constant load testing (tensile, 4-PB), constant strain testing (U-bend, C-ring), and fracture mechanics (double cantilever beam sample) are covered. Considering the variety of testing solutions, the field of search is narrowed to hot (up to 250°C) aqueous chloride solutions with dissolved H₂S and CO₂ gases under high pressure (up to 200 bar total pressure).     

On the corrosion behaviour of 8090-T6 sheet material

The exfoliation corrosion and stress corrosion cracking behaviour of an unrecrystallized sheet of the Al-Li-Cu-Mg-Zr alloy 8090-T6 was investigated. The material was highly susceptible to exfoliation corrosion in the 96 h EXCO test, whereas the intermittent salt spray test (MASTMAASIS test) revealed only a slight degree of exfoliation. The stress corrosion cracking behaviour was investigated in 3.5% NaCl solution under constant load, constant deformation, and slow strain rate conditions. Tests under constant load were also performed in an inhibited and acidified 2% NaCl solution according to the German standard LN 65666. In these accelerated tests the investigated alloy was found to be not susceptible to stress corrosion cracking in the rolling direction. The slow strain rate tests revealed a great scattering of the relative fracture energy with decreasing strain rates. This scatter is probably caused by pits acting as crack nuclei thus giving rise to scatter of the ductility.     

Comparison of accelerated SCC tests performed on the aluminium alloy 2014-T651

The stress corrosion cracking (SCC) behaviour of plates of the Al-Cu-Si-Mn-Mg alloy 2014-T651 was investigated in short transverse direction performing various accelerated tests. Corrosive media used were: aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3 (according to LN 65666), and substitute ocean water according to ASTM D1141. C-ring and tensile specimens were loaded under constant deformation, constant load and slow strain rate conditions. Alternate immersion tests in 3.5% NaCl solution clearly indicate the low SCC resistance of the alloy 2014-T651 in short transverse direction. Under continuous immersion conditions the acidified 2% NaCl solution containing chromate is an appropriate synthetic environment, while neutral 3.5% NaCl solution does not promote severe stress corrosion cracking. The SCC susceptibility of 2014-T651 is also observed in slow strain rate tests using substitute ocean water as well as acidified 2% NaCl solution inhibited by chromate. In 3.5% NaCl solution the evaluation of slow strain rate data is complicated by pre-exposure effects.     

Stress corrosion cracking of the austenitic Fe-Al-Mn alloy in chloride environment

The SCC behavior of Fe-8.7 Al-29.7Mn-1.04C alloy in a 20% sodium-chloride solution (100°C) has been investigated by the slow strain rate method. The results showed that the alloy was susceptible to SCC only at the free corrosion potential and at the applied strain rate of 2.8 × 10^?7/s. Application of the cathodic potential during the slow strain rate test resulted in the loss of ductility in the alloy which was attributed to the hydrogen induced cracking.     

Investigation of the SCC behaviour of alloy 2024 using the slow strain rate technique

The stress corrosion cracking (SCC) behaviour of 2024 plate in T351 and T851 tempers was investigated in short transverse direction performing accelerated tests under constant deformation, constant load and slow strain rate conditions. Corrosive media used were: aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH 3 (according to LN 65666), an aqueous solution of 3% NaCl + 0.3% H₂O₂, and substitute ocean water according to ASTM D1141. Alternate immersion tests in 3.5% NaCl solution indicated the low SCC resistance of the alloy 2024-T351 as well as the improved SCC behaviour due to aging to T851 condition. Similar results were obtained from constant load tests under permanent immersion conditions in the acidified chloride-chromate solution, in 3% NaCl solution with peroxide, and in substitute ocean water, whereas no SCC failure was observed with specimens which were permanently immersed in 3.5% NaCl solution. Using the slow strain rate method, 3% NaCl + 0.3% H₂O₂ and substitute ocean water were found to be effective synthetic environments. The other two electrolytes did not promote severe stress corrosion cracking with alloy 2024-T351. The SCC behaviour of 2024-T851 was difficult to determine employing the slow strain rate technique. Large scatter in data, observed even in inert environment, and the low elongation of the aged material, exacerbated by a further degradation of ductility due to pitting and intergranular corrosion, precluded an evaluation.     

低碳钢在NaNO_3溶液中的应力腐蚀开裂

<正> 对碳钢和低合金钢,特别是一系列高强钢构件,除用作与硝酸盐直接接触的化工设备外,用于氮肥厂的钢结构、混凝土中的钢筋,地下管道以及高温热风炉等都观察到过由硝酸盐引起的应力腐蚀开裂。 过去人们主要用恒载荷法或恒变形法在较高温度(90℃到沸点)和较高浓度的硝酸盐介质中研究各种因素对低合金钢或碳钢应力腐蚀开裂的影响。近来发现,在室温和含较低浓度NO_3~(?)的介质中,即使碳钢或低合金钢所受的机械应力低于屈服点也会出现应力腐蚀,并且在硝酸盐介质中除恒载荷条件下能产生应力腐蚀外,还会产生与应变率有关的应力腐蚀,它不存在阳极极化临界电位。由于以往的工作或者没有采用恒电位控制,     

6061铝合金材料常数的研究

通过热压缩试验,研究了6061铝合金材料的流动应力与温度、应变速率和应变之间的关系。根据试验数据,采用一元线性回归方法,确定了该材料的常数,如:激活能Q、应力指数n、应力水平参数α和结构因子A。研究表明,高温压缩变形时,6061铝合金的软化中动态回复是主要的;6061铝合金是正应变敏感材料。     

慢应变速率下铝合金的腐蚀行为

根据铝合金腐蚀的基本特征，建立了新鲜铝合金瞬时腐蚀速率的计算方法。通过改变试样的应变速率，研究了力学效应对LC4CS铝合金腐蚀电化学行为的影响。结果表明：在恒应变速率作用下，铝合金自腐蚀电位有明显的负移趋势，且应变速率愈大，负移速率愈快。与阳极氧化后的铝合金短路耦合，在应变量大于0.04后，LC4CS铝合金的自溶解电流显示急剧增大的趋势。对同一应变速率而言，随着应变量的增加，新鲜铝合金的瞬时腐蚀速率也随之增大。     

Sulfate‐reducing bacteria‐assisted hydrogen‐induced stress cracking of 2205 duplex stainless steels

The paper presents the results of a laboratory investigation of the microbiologically assisted hydrogen‐induced stress cracking (HISC) of 2,205 duplex stainless steel (DSS). The testing of susceptibility toward HISC was performed with two different methods. Precharged in sulfate‐reducing bacteria (SRB), inoculated medium samples were subjected to slow strain‐rate testing in artificial seawater. In situ constant load tests were performed directly in SRB‐inoculated medium under hydrogen charging at 70% of the ultimate tensile strength. Samples tested in the biotic (SRB) conditions showed a considerable loss of ductility as compared to those tested in sterile conditions. Quantitative characteristics of fracture surfaces indicated increased susceptibility to HISC of biotic samples, therefore, suggesting a role of SRB in promoting hydrogen damage of DSS.