Comparison of tensile properties of X60 pipeline steel tested in high pressure gaseous hydrogen using tubular and conventional specimen

Developing engineering standards for the hydrogen economy requires extensive materials testing at relevant operating conditions, i.e. in gaseous hydrogen at various pressures and temperatures. One method to satisfy the need for a high and affordable output of test results is materials testing using tubular specimens where the hydrogen pressure is applied inside the tube. This study focused on the comparison of tensile properties of X60 pipeline steel tested in high pressure gaseous hydrogen using tubular (TS) and conventional specimen (CS) tested in an autoclave. The reduction of area (RA) of TS showed comparable trends known from literature for CS upon a variation of strain rate and residual oxygen content. However, when the identical X60 steel was tested in ambient air, RA of the TS was lower compared to the CS. When tested in hydrogen, RA of the TS is higher compared to the CS. Both could be interpreted and explained by differences in the necking behavior, with and without hydrogen.     

Resistance of pearlite against hydrogen-assisted fatigue crack growth

Recent progress in realizing hydrogen society requires higher-strength steels having decent hydrogen embrittlement resistance via optimized microstructural controls. The present communication first reports the fatigue crack growth (FCG) property of pearlitic steel in a high-pressure, i.e., 90 MPa, hydrogen gas environment to probe this standard microstructure's potency for becoming a constructive reinforcing agent in future hydrogen-compatible structural materials. As-transformed eutectoid steel with 1080 MPa-tensile strength exhibited hydrogen-induced FCG acceleration to a lesser extent relative to martensite with an equivalent strength level and occasionally to pure ferritic iron. Furthermore, the superiority over martensite was augmented under slow loading-rate conditions, suppressing time-dependent cracking, a critical issue in implementing defect tolerant design on high-strength steels for hydrogen gas applications.     

Insight into hydrogen effect on a duplex medium-Mn steel revealed by in-situ nanoindentation test

Medium-Mn steel is the newly developed steel acting as a promising candidate of the 3rd-generation advanced high strength steels. In the present study, the effect of hydrogen on the mechanical behavior and martensite transformation process in a duplex medium-Mn steel is investigated by in-situ nanoindentation test. The mechanical response of individual phase: ferrite, and retained austenite by introducing hydrogen is studied. With the presence of hydrogen, the reduction of activation energy for dislocation nucleation was verified by using a stress-biased, statistical thermal activation model. The stacking fault energy (SFE) was reduced, which was revealed by electron channeling contrast (ECC) technique. Magnetic force microscopy (MFM) revealed a suppression of retained austenite to α′-martensite transformation with the presence of hydrogen, which is related to hydrogen induced SFE reduction and enhanced slip planarity.     

半导体绿激光血管内照射治疗血管性痴呆与阿尔茨海默病的疗效比较

比较半导体绿激光血管内照射治疗血管性痴呆和阿尔茨海默病的临床疗效。对住院30例老年期痴呆患者分为二级,17例血管性痴呆(VD组),13例阿尔茨海默病(AD组),二组同时进行绿激光血管内照射治疗,在治疗前后,二组分别作血液流变学,神经心理测验以及TCD、EEG、EKG等实验室检查比较。结果二组在治疗后,全血粘度、血浆粘度、红细胞聚集指数等血液流变学指标均有显著下降(P＜0.01),神经心理测验MMSE、APL、HDS等也均有明显改善(P＜0.01)。但二组同无明显差异(P＜0.05)。半导体绿激光血管内照射疗法可改善血管性痴呆和阿尔茨海默病患者的血液流变学指标和改善临床症状。     

X90管线钢母材和焊缝在近中性模拟溶液中不同加载电位下的应力腐蚀行为

X90是继X80和X100管线钢后开发的新一代管线钢,已成为国内外研究的新热点。为了深入了解加载电位对X90管线钢土壤应力腐蚀行为的影响,采用电化学测试和慢应变速率拉伸试验(SSRT)的方法研究了X90管线钢直缝焊管母材和焊缝在近中性模拟溶液(NS4)中不同加载电位下的应力腐蚀行为,应用扫描电子显微镜(SEM)对其断口形貌进行了观察,分析应力腐蚀行为的机理。研究结果表明:(1)NS4溶液中的X90管线钢直缝焊管母材、焊缝的极化曲线均表现为阳极溶解特征,无活化—钝化现象;(2)X90管线钢直缝焊管母材和焊缝在NS4溶液中具有一定的应力腐蚀敏感性,随着加载电位的负移,用延伸率的损失率和断面收缩率的损失率表示的应力腐蚀敏感性指标先减小后增大,焊缝的应力腐蚀敏感性大于母材的应力腐蚀敏感性;(3)X90管线钢直缝焊管母材和焊缝在NS4溶液中的应力腐蚀开裂行为存在以下3种机制——外加电位为EOCP的阳极溶解机制、外加电位为-850 mV的阳极溶解+氢脆机制、外加电位为-1 000 mV和-1 200 mV的氢脆机制。结论认为,该研究成果可以为X90管线钢的大规模使用提供技术支撑和理论依据。     

Environmental sensitivity and mechanical behavior of boron-doped Fe–45at.%Al intermetallic in the temperature range from 77 to 1000 K

The tensile properties and fracture behavior of a coarse-grained (grain size 420 μm) Fe–45at.%Al intermetallic doped with 0.05 at.% boron were examined at ambient temperature in air, argon and vacuum as well as in the 77–1000 K temperature range in liquid nitrogen, dry ice and air. Before testing the alloy was low temperature annealed (vacancy annealed) in order to remove all the retained vacancies. At ambient temperature ductility increases accordingly to decreasing water vapor (moisture) content in each environment. The mixed transgranular cleavage (TGC)+intergranular failure (IGF) mode in vacuum, which is associated with the highest elongation (6%), exhibits around 40% of IGF and the mixed fracture mode in argon, which is associated with the second highest elongation (3.2%), exhibits 15% of IGF. The TGC fracture mode in air is associated with the lowest elongation (1%). Elongation in the cryogenic temperature range from 77 to 213 K is very low being in the range from 0.6 to 2.8%, and is associated with a mixed transgranular+intergranular fracture mode. Elongation increases gradually from 300 to 800 K attaining a ductility peak at 800 K and then decreases rapidly with increasing temperature. At 600–800 K, the yield strength of Fe–45Al–0.05B exhibits anomalous temperature dependence with the yield strength peak at 800 K. The mode of fracture from 300 to 700 K is predominantly TGC and that at the ductility peak is ductile rupture with very deep dimples. At temperatures above 800 K the mode of fracture changes to a typical intergranular creep (fibrous) failure with numerous flat dimples (voids/cavities) at the grain boundary facets, which is associated with a tensile ductility drop. Fine particles (borides) are observed at the grain boundary facets, which assist the development of intergranular creep fracture.     

Hydrogen embrittlement property of a 1700-MPa-class ultrahigh-strength tempered martensitic steel

The hydrogen embrittlement property of a prototype 1700-MPa-class ultrahigh-strength steel (NIMS17) containing hydrogen traps was evaluated using a slow strain rate test (SSRT) after cathodic hydrogen precharging, cyclic corrosion test (CCT) and atmospheric exposure. The hydrogen content in a fractured specimen was measured after SSRT by thermal desorption spectroscopy (TDS). The relationship between fracture stress and hydrogen content for the hydrogen-precharged specimens showed that the fracture stress of NIMS17 steel was higher, at a given hydrogen content, than that of conventional AISI 4135 steels with tensile strengths of 1300 and 1500 MPa. This suggests better resistance of NIMS17 steel to hydrogen embrittlement. However, hydrogen uptake to NIMS17 steel under CCT and atmospheric exposure decreased the fracture stress. This is because of the stronger hydrogen uptake to the steel containing hydrogen traps than to the AISI 4135 steels. Although NIMS17 steel has a higher strength level than AISI 4135 steel with a tensile strength of 1500 MPa, the decrease in fracture stress is similar between these steels.     

氢对钛合金的影响

介绍了钛合金的基本性质,分析了钛合金氢脆机理及表现,概括了氢对钛合金裂纹扩展速率和疲劳寿命的影响,总结了氢致裂纹的影响因素。     

30CrMnSiNi2A螺栓断裂分析

材料为30CrMnSiNi2A的一螺栓在正常装配预紧时断裂。经化学分析、宏微观检验,认为,螺栓的断裂系氢脆所致。