低活化马氏体钢热等静压焊接接头性能初步研究

研究了低活化马氏体钢(CLF-1)热等静压(HIP)焊接接头的性能,经980℃/1h/空冷+740℃/2h/空冷的性能热处理后,接头组织保持着CLF-1钢母材回火马氏体组织;常温拉伸性能与母材相当,断口为韧窝状且有第二相粒子产生,为塑性断裂且断于焊缝;常温冲击功最高为母材的26.2%。初步分析认为焊接表面制备状态、表面污染物、表面清洗状态、表面氧化膜都会影响基体原子充分扩散,导致界面扩散层不均匀,焊缝裂纹敏感性增强,冲击功低,且不稳定。     

低活化马氏体钢热等静压焊接接头性能初步研究

研究了低活化马氏体钢(CLF-1)热等静压(HIP)焊接接头的性能,经980℃/1h/空冷+740℃/2h/空冷的性能热处理后,接头组织保持着CLF-1钢母材回火马氏体组织;常温拉伸性能与母材相当,断口为韧窝状且有第二相粒子产生,为塑性断裂且断于焊缝;常温冲击功最高为母材的26.2%。初步分析认为焊接表面制备状态、表面污染物、表面清洗状态、表面氧化膜都会影响基体原子充分扩散,导致界面扩散层不均匀,焊缝裂纹敏感性增强,冲击功低,且不稳定。     

低活化铁素体/马氏体钢CLF-1激光焊接模式转变研究

为研究低活化铁素体/马氏体钢(RAFM) CLF-1激光焊接模式转变规律,对其焊缝横截面形貌及尺寸进行了宏观表征和定量分析。结果表明,在一定条件下,随着焊接功率的增大,焊接模式从热传导焊模式向小孔深熔焊模式转变,焊缝横截面表现为“圆弧形”、“V字形”和“钉头形”三种类型形貌。CLF-1钢激光焊接模式不受焊接速度、离焦量变化的影响。激光焊接模式转变的临界值为深熔焊阈值,CLF-1钢深熔焊阈值由材料自身特性决定,当焊接速度为10mm·s^-1时,CLF-1钢深熔焊阈值约为1.20kW·mm^-1。     

钨/低活化钢钎焊用铁基非晶钎料与接头微结构

为了连接W和CLF-1 RAFM钢,设计出由低活化元素组成的Fe-B-Si、Fe-B-Si-Sn、Fe-B-Si-Cr-(Sn)、Fe-B-Si-P-(Cr,Sn)、Fe-B-Si-Mn-(Ga,Sn)和Fe-B-Si-(Cr,Mn,Ga,Ta,Sn)系列Fe基非晶钎料,结合熔体快淬技术制备出非晶合金箔带,并对W/CLF-1 RAFM钢接头微结构进行了对比研究。采用X-射线衍射仪对箔带样品与焊缝进行了相鉴定;通过差热分析测量了非晶箔带的熔化温度和液相线温度;利用光学金相和电子探针分析了焊缝组织形貌和元素分布。结果表明,利用Fe-B-Si、Fe-B-Si-Cr和Fe-B-Si-Mn-Sn非晶钎料可获得结构完整的W/CLF-1钢接头;前两种钎料得到的焊缝组织基体相为α-Fe固溶体,而含Mn钎料形成的焊缝基体为马氏体组织;在高温钎焊过程中,这些Fe基非晶钎料中的高B含量促使FeWB、FeW2B2和Fe3B型金属间化合物在焊缝中形成,并有效地阻止了W元素向低活化钢基体长程扩散。所设计的低活化Fe基非晶钎料可用于W和低活化钢的连接和接头性能研究。     

液态锡对低活化马氏体/铁素体钢CLF-1的腐蚀行为研究

采用背散射电子扫描显微镜、电子衍射能谱和X射线衍射等分析方法,研究了浸泡在300~700℃的液态锡(Sn)中24h后的低活化马氏体/铁素体钢CLF-1的腐蚀行为。研究结果表明,在所有测试温度下液态锡对CLF-1钢表面均有不同程度的腐蚀,主要腐蚀机制为化合溶解腐蚀。铬(Cr)以单质形式溶解沉淀,液态锡与铁在CLF-1钢表面反应生成由铁锡化合物构成的腐蚀层。当温度低于500℃时,腐蚀层厚度近似为一常量,约8μm,化学成分为FeSn₂。当温度高于500℃时,腐蚀层厚度随温度线性增加,腐蚀层呈双层结构,分别为CLF-1边界处的FeSn层和覆盖在其表面的FeSn₂层。     

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基于中国氦冷固态实验包层模块(CH-HCSB-TBM)的新设计方案,采用蒙特卡罗粒子输运程序MCNP和欧洲活化计算程序FISPACT,对CH-HCSB-TBM进行了三维活化计算分析.计算结果表明,停堆初期TBM总的放射性活度、衰变余热分别为1.78× 1016Bq和3.01kW,主要受结构材料CLF-1影响.同时给出了影响TBM材料活化特性的主要核素及其生成途径,为TBM设计的材料选取和优化提供依据.根据计算的停堆剂量率可知,TBM中的活化材料都能采取远程操作实现再循环利用,可有效防止放射性环境危害问题.     

聚变堆用CLF-1 钢与316L 钢TIG 焊接接头组织与性能初步研究

对用W19123L 为焊丝的聚变堆用低活化CLF-1 钢与316L 钢的钨极氩弧焊(TIG)焊接接头金相组织及性能进行了初步研究。结果表明：焊接接头成型良好、无缺陷;金相组织表明焊接接头由CLF-1 侧(母材区、热影响区、熔合区)、过渡层、焊缝区、316L 侧(母材区、热影响区、熔合区)组成;室温拉伸试验结果优于母材的最低要求值;弯曲试验后的焊接接头内外表面完好,无裂纹产生,变形均匀;焊接接头冲击值成凹型分布,焊缝区冲击值最低,焊缝两侧热影响区冲击值次之,母材冲击值最高,316L 侧冲击值略高于CLF-1 侧,均满足焊接接头设计值;焊接接头上表面1.6mm 硬度波动较大,略高于1/2T 和下表面1.6mm 处,焊接接头1/2T 和下表面1.6mm 硬度分布较均匀,从CLF-1 侧到316L 侧有下降趋势。整体焊接性能基本稳定,满足异种钢焊接性能匹配要求。     

聚变堆用结构材料CLF-1研究进展

本文报道了我院近半年来低活性铁素体／马氏体钢CLF-1的研究进展。通过微观组织观察和室温拉伸性能测试，证明该钢已具有优于Eurofer97的室温拉伸性能，而且得到了全马氏体的微观组织。     

JLF-1钢高温循环变形后硬度与微观结构的数值关系

高温循环变形是结构材料性能降级的主要原因之一.用透射电子显微镜对低活化铁素体/马氏体钢——JLF-1钢低周疲劳样品的微观结构进行了分析,并测试了循环变形前后此钢显微维氏硬度的变化.为了掌握JLF-1钢性能在高温循环变形中的变化机理,依据位错理论,用最小二乘法对高温循环变形后的显微维氏硬度与微观结构进行了回归计算,得到了此钢显微维氏硬度与板条尺寸、位错胞尺寸、位错密度的数值关系. 关键词： 低活化铁素体/马氏体钢 循环变形 微观结构 显微维氏硬度     

聚变堆候选金属材料的惰性气体离子辐照损伤的研究

综述了有关核聚变反应堆材料的辐照损伤问题的研究,主要包括国产316L奥氏体不锈钢中氦的扩散与氦泡形核生长的研究、316L及低活化FeCrMn合金的高能Ar离子辐照缺陷与空洞肿胀的研究、近期开展的低活化马氏体钢和氧化物颗粒弥散强化合金的高能Ne离子辐照损伤和效应的研究成果。This paper gives a review of our recent studies on the irradiation damage induced by energetic inert-gasions in metallic materials candidate to fusion reactors. The work includes the study of helium diffusion and helium bubble formation in 316L stainless steels, the study of void formation and swelling in the low-activation Fe-Cr-Mn alloy irradiated with high-energy Ar ions, the study of irradiation damage in some low-activation Fe-based steels and ODS alloys by high-energy Ne ions.     

Effect of annealing prior to cold rolling on magnetic and mechanical properties of low carbon non-oriented electrical steels

The effects of annealing prior to cold rolling on the microstructure, magnetic and mechanical properties of low-C grain non-oriented (GNO) electrical steels have been investigated. The grain structure of hot-rolled electrical steel strips is modified by annealing at temperatures between 700 and 1050 °C. Annealing at temperatures less than the ferrite to austenite+ferrite transformation temperature on heating (Ac₁) causes a marginal effect on the grain size. However, annealing in the intercritical region at temperatures between Ac₁ and Ac₃ (the ferrite+austenite to austenite transformation temperature on heating) causes rapid decarburization and development of large columnar ferrite grains free of carbide particles. This microstructure leads, after cold rolling and a fast annealing treatment, to carbide free, large ferrite grain microstructures with magnetic and mechanical properties superior to those observed typically in the same steel in the industrially fully processed condition. These results are attributed to the increment in grain size and to the {1 0 0} fiber texture developed during the final annealing at temperatures up to 850 °C. Annealing at higher temperatures, T>Ac₃, results in a strong {1 1 1} fiber texture and an increase of the quantity of second phase particles present in the microstructure, which lead to a negative effect on the final properties. The results suggest that annealing prior to cold rolling offers an attractive alternative processing route for the manufacture of fully processed low C GNO electrical steels strips.     

Thermal stability of the microstructure of 12% chromium ferritic–martensitic steels after long-term aging at high temperatures

The structure of EK-181 (RUSFER-EK-181, low-activation) and ChS-139 12% Cr ferritic–martensitic steels is investigated and their mechanical properties are tested after long-term (13500 h) aging at 450 and 620°C. The microstructure of the steels exhibits a high thermal stability, which provides the retention of their initial short-term mechanical properties at test temperatures.     

高温高压下碳化钨晶体的结构、力学、电子、光学以及热力学性能的第一性原理计算

本文利用密度泛函理论中的广义梯度近似对碳化钨晶体的三种结构(碳化钨相、闪锌矿相以及纤锌矿相)进行了优化,得到能量最低的稳定构型,并在此基础上计算了它的力学、电子、光学和高温高压下的热力学性质.研究表明:在0～300 GPa压力范围内,碳化钨相具有最高的稳定性.同时,高压下碳化钨相的弹性常数满足Born-Huang准则,且0 GPa和300 GPa下的声子色散没有虚频,证明了高压下碳化钨相的静力学稳定性和动力学稳定性.电子性质表明了碳化钨的金属性.光学性质表明碳化钨在高能区很难吸收光.热力学性质的研究表明:体积比V/V_0对压强的变化更敏感;高温时C_V曲线近似一条直线;给定压强下热膨胀系数α在600 K温度以上增长非常缓慢;压强对德拜温度Θ_D的影响较大;在低压下格林艾森系数γ的变化较大.     

Magnetic properties of stainless steels at room and cryogenic temperatures

The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77 K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite having harder magnetic properties than fully annealed steels some of the as-received steels still display soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found to affect the permeability and coercive force, with lower-carbon steels displaying significantly higher permeability and lower coercive force. The decrease in coercive force with reduced carbon content is attributed to fewer carbide inclusions which inhibit domain wall motion. Cooling to 77 K resulted in harder magnetic properties. Averaged over the ten steels tested the maximum permeability decreased by 8%, the coercive force increased by 14%, and the residual and saturation flux densities increased by 4% and 3%, respectively. The change in coercive force when cooled is comparable to the theoretical prediction for iron, based on a model of domain wall motion inhibited by inclusions. The modest changes of the magnetic properties indicate that the stainless steels can still be used in magnetic applications at very low temperatures.     

Structural amorphous steels

Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist's dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.     

Helium and point defect accumulation: (i) microstructure and mechanical behaviour

Ferritic/martensitic (F/M) steels are good candidate structural materials for the future fusion reactors and spallation sources. However, irradiation of steels is known to produce hardening, loss of ductility, shift in ductile to brittle transition temperature (DBTT) and reduction of fracture toughness and creep resistance starting at low doses. Helium (He), produced by transmutation during the irradiation, also impacts mechanical properties. Numerous experimental and theoretical studies on the evolution of the microstructure of steels under irradiation have been conducted until now. We review the effect of irradiation-induced point defects and in particular of He on the mechanical properties of F/M steels. To cite this article: R. Schäublin et al., C. R. Physique 9 (2008).     

Peculiar Features of Thermal Aging and Degradation of Rapidly Quenched Stainless Steels under High-Temperature Exposures

This article presents the results of comparative studies of mechanical properties and microstructure of nuclear fuel tubes and semifinished stainless steel items fabricated by consolidation of rapidly quenched powders and by conventional technology after high-temperature exposures at 600 and 700°C. Tensile tests of nuclear fuel tube ring specimens of stainless austenitic steel of grade AISI 316 and ferritic–martensitic steel are performed at room temperature. The microstructure and distribution of carbon and boron are analyzed by metallography and autoradiography in nuclear fuel tubes and semifinished items. Rapidly quenched powders of the considered steels are obtained by the plasma rotating electrode process. Positive influence of consolidation of rapidly quenched powders on mechanical properties after high-temperature aging is confirmed. The correlation between homogeneous distribution of carbon and boron and mechanical properties of the considered steel is determined. The effects of thermal aging and degradation of the considered steels are determined at 600°C and 700°C, respectively.     

Structure and properties of high-strength iron-nickel maraging steels

The effect of structural changes on the physicomechanical properties of high-strength maraging steels based on iron-nickel-titanium and iron-nickel-aluminum systems after different types of treatment is investigated. It is shown that economically alloyed cobalt-free maraging steels acquire a combination of high mechanical and magnetic properties and resistance to low-cycle fatigue.     

Physical and Mechanical Properties of W-Ni-Fe-Co Metal Foam Modified by Titanium Tungsten Carbide Alloying

Russian Physics Journal - The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the...     

Comprehensive Analysis of Nanostructure of Oxide Dispersion Strengthened Steels as Prospective Materials for Nuclear Reactors

Physics of Atomic Nuclei - The enhanced mechanical properties of oxide dispersion-strengthened (ODS) steels are mainly due to the high density of homogeneously distributed oxide inclusions. It is...