小冲杆技术及其在材料与铅铋脆化效应研究中的应用

第四代反应堆中铅冷快堆是一种非常有发展前景的堆型。在铅冷快堆包壳材料设计时,需要重点考虑包壳材料与高温铅铋的相容性,关注其抗液态金属腐蚀能力,尤其是腐蚀介质与应力耦合时材料性能的变化。小冲杆实验(SPT)是一种使用小尺寸样品评估材料服役条件下力学性能变化的实验方法,这种方法可以直接在正在使用的材料中提取样品而不损害其完整性,因此小冲杆测试非常适用于所研究材料数量有限或研究在役材料的情况。本文简要介绍了小冲杆测试技术,归纳了小冲杆测试与标准尺寸测试实验的相关性,阐述了使用小冲杆技术进行的关键材料力学性能研究,特别阐述了小冲杆测试在研究结构材料液态金属脆化效应(LME)方面的应用。结果可为小冲杆技术应用于研究材料液态铅铋脆化效应提供技术方法及理论支持。     

T91钢TIG+MIG焊接接头性能及组织

对采用TIG＋MIG焊的T91钢焊接接头进行了力学性能、持久强度和高温时效试验,并对T9l钢TIG＋MIG焊接接头的显微组织及断口的断裂特征进行了观察和分析。结果表明,T91钢TIG＋MIG焊接接头的韧脆转变温度（FATT）为-13℃,625℃l7958h高温持久试验为70MPa,外推10^5h高温持久强度为46．48MPa。焊接接头的高温性能取决于其组织的变化,以M23C6为主的合金碳化物对持久强度起了重要作用。     

铅铋合金提纯用316L坩埚失效行为分析

使用316L坩埚对铅铋合金进行提纯处理6~7个月后,坩埚底部出现穿孔现象,侧壁减薄明显。利用XRD、SEM-EDS、LCM和体视显微镜对失效316L坩埚表面形貌、截面组分进行观察分析,结合使役环境分析失效原因。结果表明:在600 ℃待提纯液态铅铋合金中,316L坩埚发生严重的溶解腐蚀和氧化腐蚀;表面形成能有效保护基体的不均匀氧化层;未被氧化层保护的区域Sb元素富集,基体材料以大块物质剥落的形式进行溶解;基体内部出现蚀孔,蚀孔达到临界尺寸或在外力作用下,边缘处裂纹形核并长大,Sb元素沿裂纹扩展通道向基体内部渗透富集并溶解基体。     

汽车用AZ91镁合金的耐腐蚀性能

以AZ91镁合金为研究对象,研究了NaCl溶液的浓度、腐蚀时间、温度和搅拌速度对AZ91镁合金耐腐蚀性的影响。利用扫描电镜观察了腐蚀后的表面形貌和横截面形貌,定性分析了AZ91镁合金在NaCl溶液中的腐蚀行为。结果表明,随NaCl溶液浓度、腐蚀时间、温度和搅拌速度增加,AZ91镁合金腐蚀速率主要呈递增趋势,且腐蚀形式为沿晶腐蚀。     

不同表面处理对316L钢焊缝耐液态铅铋腐蚀的影响

设计制造了一套耐高速流液态金属腐蚀试验装置,用以研究分别用不同号数砂纸打磨和不同抛光处理后的316L钢焊缝在550 ℃的流动(相对流速为2.62 m/s)液态铅铋合金中的腐蚀情况。研究发现各组试样都形成了双氧化层结构,内层主要为较疏松的Fe3O4,外层主要为较致密的FeCr2O4;表面粗糙度越小,元素传质过程越慢,高速流动的液态LBE磨蚀作用越小,316L钢焊缝的耐蚀性越好。     

电站锅炉用T91钢热穿孔性能的研究

对T91钢的高温塑性和穿孔性能进行了试验研究。研究表明:在1100～1200℃温度范围内,该钢具有良好的塑性;在1100～1250℃温度范围内具有良好的穿孔性能。     

T91钢老化后组织与性能研究

研究了T91钢经加速老化后的组织与性能的变化.结果表明,随老化温度、时间、载荷的增加,形成的碳化物网越来越严重,材料的抗拉强度、冲击韧性、硬度下降.经老化后T91钢中的碳化物颗粒粗化且向晶界聚集,晶内碳化物减少.与原材料相比,老化后T91钢试样的冲击断El的准解理区域明显增大.     

工艺参数及焊接材料对T91/P91钢焊缝性能的影响

综合分析了手工电弧焊焊接过程中的预热温度、热处理温度、焊接线能量等主要工艺因素以及焊接材料对T91/P91钢焊缝性能的影响。     

工艺参数及焊接材料对T91/P91钢焊缝性能的影响

综合分析了手工电弧焊焊接过程中的预热温度、热处理温度、焊接线能量等主要工艺因素以及焊接材料对T91／P91钢焊缝性能的影响。     

焊接热循环对T92钢组织脆化的影响

采用Gleeble—3800热模拟试验机对T92钢进行不同峰值温度的焊接热循环试验,并对试验试样进行室温冲击韧性试验.借助光学显微镜分析其微观组织,用扫描电镜观察其冲击试样断口形貌特征.结果表明,T92钢焊接加热温度在900℃以上易因奥氏体晶粒粗大导致其组织脆化,断口呈现典型的准解理形貌特征,而在900℃以下的焊接加热仍能保持较好的室温冲击韧性,断口呈现均匀细小的韧窝断口特征;T92钢中高含量的强碳、氮化物形成元素高温状态重新固溶后,在奥氏体中的扩散速度滞后于晶界的迁移速度,进而产生过饱和的室温组织是引起组织脆化的直接原因.     

Effect of oxygen on liquid sodium embrittlement of T91 martensitic steel

The liquid sodium embrittlement susceptibility of the T91 steel in a standard metallurgical state has been studied with varying dissolved oxygen levels. The experimental procedure consists of a pre-exposure wetting step in static sodium before mechanical testing in liquid sodium. The oxygen impurity plays the role of a wetting promoter that facilitates LME of the T91 steel rather than taking part in the fracture process. Brittle grain boundary decohesion is observed using transmission electron microscopy on focused ion beam prepared foils. This settles the issue about the susceptibility of steels to liquid metal embrittlement in liquid sodium.     

Effect of heat treatment on liquid sodium embrittlement of T91 martensitic steel

The sensitivity to liquid sodium embrittlement, in the temperature range of 300–550 °C, of T91 martensitic steel has been studied according to tempering temperature. In air, the T91 steel is ductile. A ductile to brittle transition induced by liquid sodium has been observed. Liquid sodium acts as well on the crack initiation period as on the crack propagation one. In absence of external defect, it is found that sodium affects grain boundary strength and initiates an intergranular crack which then propagates by cleavage in the bulk.     

A review of steel corrosion by liquid lead and lead-bismuth

Liquid metal technologies for liquid lead and lead-bismuth alloy are under wide investigation and development for advanced nuclear energy systems and waste transmutation systems. Material corrosion is one of the main issues studied a lot recently in the development of the liquid metal technology. This study reviews steel corrosion by liquid lead and lead-bismuth, including the corrosion inhibitors and the formation of the protective oxide layer. The available experimental data are analyzed by using a corrosion model in which the oxidation and scale removal are coupled. Based on the model, long-term behaviour of steels in liquid lead and lead-bismuth is predictable. This report provides information for the selection of structural materials for typical nuclear reactor coolant systems when selecting liquid lead or lead-bismuth as heat transfer media.     

Liquid metal embrittlement susceptibility of T91 steel by lead–bismuth

Previous studies on T91 steel in its standard metallurgical state do not provide evidence for liquid metal embrittlement by eutectic Pb–Bi. In this paper, we show that this steel can be embrittled by Pb–Bi when direct contact between the steel and the liquid metal is obtained by prior ion beam sputtering of the native oxidized film.     

Suppression of liquid metal embrittlement in resistance spot welding of TRIP steel

ABSTRACT

Third-generation advanced high strength steels are typically given a zinc coating that provides excellent resistance to corrosion. During the resistance spot welding process, the melted zinc coating enables liquid metal embrittlement (LME) that causes cracking in the weld indent. In this study, LME in TRIP 1100 and TRIP 1200 steels was suppressed by placing aluminium interlayers added between the electrode and steel contact surface. Compared to welds exhibiting LME, TRIP 1100 with aluminium interlayers showed complete strength recovery while TRIP 1200 with aluminium interlayers resulted in a recovery of strength by 90%. Aluminium interlayers suppress LME by the formation of iron aluminides that hinder liquid zinc from coming in contact with the steel substrate, thus preventing LME.     

Mechanical behavior of coated T91 steel in contact with lead-bismuth liquid alloy at 300 °C

Different coatings, deposited by pack cementation process, were developed to protect the T91 steel against dissolution by Lead Bismuth Eutectic (LBE): iron aluminide, iron boride and an iron solid solution enriched in chromium and covered by carbide. The mechanical behavior of the T91 steel with the different coatings is studied in air and in LBE at 300 °C by the use of the Small Punch Test (SPT). Though the coatings are brittle, they do not affect the mechanical strength of the substrate in air, except the iron boride one. In LBE, the most critical situation is found when fracture of the interface between the T91 steel and the coating occurs. Then, the coating provides the set of conditions to trigger liquid metal accelerated damage.     

Impact of liquid metal embrittlement cracks on resistance spot weld static strength

ABSTRACT

Advanced high strength steels used in automotive structural components are commonly protected using zinc coatings. However, the steel/zinc system creates the potential for liquid metal embrittlement (LME) during welding. Although LME cracks are known to form, limited research has found any detrimental impact of LME cracks on weld strength. In this work, a comparison of zinc coated and uncoated advanced high strength steel joints showed LME decreased strength in welds from transformation induced plasticity type microstructures and an 1100?MPa ultimate tensile strength by 43.6%. LME cracks were observed to propagate until final fracture. However, only cracks located in the periphery of the weld area were found contribute to a loss in strength.     

不损害耐蚀性的奥氏体不锈钢渗碳强化技术研究进展

奥氏体不锈钢广泛用于制造在腐蚀环境下服役的零部件和构件,但因其强度较低,应用领域受到很大限制。通过对奥氏体不锈钢的耐蚀机制分析,论述了常规渗碳对其腐蚀性能的影响,介绍了当前国内外在不损害其耐蚀性的条件下进行低温强化的技术现状,最后展望了低温渗碳耐蚀强化技术的应用前景。     

超纯铁素体不锈钢及其抗应力腐蚀研究进展

介绍了合金元素对超纯铁素体不锈钢的影响及其冶炼方法、轧制及热处理制度研究现状,分析了抗应力腐蚀影响因素,并对其在石油天然气等工业领域中的应用前景进行了预测与展望。     

镀锌Q & P980钢电阻点焊接头液态金属脆裂纹的影响因素分析

新一代超高强Q&P淬火延性钢在具有高强度的同时具有较好的断后伸长率,在车身制造中具有广阔的应用前景.然而在对镀锌Q&P980钢进行电阻点焊试验后,在焊接接头中发现了表面裂纹,前期研究表明该表面裂纹是由液态金属脆化机制所引起的,即钢板在液态锌和应力的共同作用下发生的沿晶界开裂.结果表明,点焊中的工艺参数,包括焊接电流、焊接时间及电极压力、以及加工条件,包括电极端面形状、加压模式、电极对中度均会对接头中的液态金属脆裂纹产生不同程度的影响,因此可以通过调整工艺参数及加工条件来降低裂纹的敏感性.