Zr-Sn-Nb-Fe锆合金耐腐蚀性能研究

采用静态高压釜研究了去应力态和再结晶态的SZA-4(Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge)、SZA-6(Zr-0.5Sn-0.5Nb-0.3Fe-0.015Si)锆合金以及去应力态的参比合金A(Zr-1Sn-1Nb-0.1Fe)在360℃/18.6MPa去离子水、360℃/18.6 MPa/0.01 mol·L~(-1)含锂水和400℃/10.3 MPa过热蒸汽3种条件下的耐腐蚀性能,采用扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察分析合金的微观结构。结果表明:在3种腐蚀条件下,SZA-4和SZA-6的耐腐蚀性能均明显优于参比合金A,相同腐蚀条件下,再结晶态的SZA-4耐腐蚀性能优于去应力态,而SZA-6表现出相反规律;SZA-4中存在2种密排六方结构(HCP)的第二相,一种为尺寸较小的Zr(NbFeCr)_2,另一种为尺寸较大的Zr(NbFeCr Ge)_2;SZA-6中存在着面心立方结构(FCC)的(ZrNb)_2Fe和密排六方结构(HCP)的Zr(NbFe)_2两种第二相。探讨了合金成分和第二相对3种Zr-Sn-Nb锆合金耐腐蚀性能的影响机理,认为合金成分是引起耐腐蚀性能差别的主要原因。     

PWR燃料元件包壳新型锆合金的堆外性能(英文)

发展了两种新型锆合金(N18,N36)作为PWR燃料元件包壳材料。研究了N18,N36两种锆合金的堆外性能。研究表明,具有均匀弥散分布的细小β-Nb或Zr(Fe,Cr)2第二相粒子的新合金表现出最好的抗腐蚀性能,N18和N36合金都有优良的耐腐蚀性能。合金的吸氢行为与其腐蚀行为成对应关系,而两种新型锆合金的吸氢比Zr-4合金的低。两种新锆合金的拉伸强度、爆破和蠕变性能也优于Zr-4合金。此外,两种新锆合金的热物理性能、织构和应力腐蚀行为相当或优于Zr-4合金。     

Nb、Cu对新型高温锆合金α/β相变温度和腐蚀性能的影响

研究不同元素含量的Zr-Nb-Cu合金的显微组织和其在500℃、10.3 MPa过热蒸汽中的耐腐蚀性能,结果表明,在500℃、10.3 MPa过热蒸汽中,Zr- 1.0Nb-0.05Cu合金的耐腐蚀性能最好,其耐腐蚀性能远远优于Zr-4和N18合金.在Zr-Nb-Cu合金中形成富含Nb、Fe、Cr的第二相粒子,这是影响锆合金耐腐蚀性能的一个原因.Zr-Nb-Cu合金在差热扫描量热仪分析的升温过程中,腐蚀产生的氢化物溶解,温度达到氢致α/β相变温度(约550℃)时开始β相变.添加Nb可以降低合金发生氢致β相变的温度,而增加Cu含量,可以降低合金腐蚀时的吸氢量,同时也使合金的耐腐蚀性能得到明显的提高.     

我国高性能锆合金的发展

文章介绍锆合金开发与研究的现状,着重概述我国高性能锆合金的发展.我国在跟踪国际锆合金发展的同时,通过对改善锆-4合金耐腐蚀性能的研究,研制出了具有工艺代表性的改进型锆-4合金包壳材料,且开发了两种新型锆合金.新型锆合金的堆外性能研究结果表明,它们的抗疖状腐蚀和抗吸氢性能优于锆-4合金,其他性能好于或与锆-4合金相当,综合性能明显优于锆-4合金.     

钒合金的氢致硬化和氢脆

通过气相渗氢后的室温拉伸试验,测试了多种钒合金材料的拉伸性能,如V-4Ti、V-6W-lTi和V-4Cr-4Ti,以及日本国立核聚变研究所研制的V-4Cr-4Ti合金,研究了钒合金的氢脆行为及其影响因素.实验结果表明钒合金有较强的吸氢能力,合金元素Ti能显著提高合金的吸氢量.在达到氢致脆性断裂前,氢致强化表现为典型的固溶强化,而其强化能力因Ti的存在而显著降低,是含Ti钒合金具有优良抗氢脆性能的主要原因.合金氧含量极大地影响合金的抗氢脆能力.氧含量在200～400 μg/g时,V-4Cr-4Ti合金发生氢脆断裂的临界氢含量约为300 μg/g,而当氧含量超过700 μg/g时,该临界值低于50 μg/g.另一方面,强度较低的V-4Ti合金似乎具有更好的抗氢脆能力.     

燃料棒腐蚀和吸氢模型研究

锆合金包壳的腐蚀和吸氢性能是影响燃料棒堆内性能的重要因素。本文在锆合金包壳均匀腐蚀吸氢基本机理和现有模型的基础上,结合某特定燃料棒包壳材料的具体情况和使用特点,建立了包壳材料的均匀腐蚀和吸氢模型,并根据现有辐照数据对所建立的模型进行了验证。     

热处理工艺与合金成分对国产新锆合金拉伸性能及显微组织的影响

采用MTS材料试验机研究了去应力态和再结晶态的SZA4(Zr-0.8Sn-0.25Nb-0.35Fe-0.1Cr-0.05Ge)、SZA6(Zr-0.5Sn-0.5Nb-0.3Fe-0.015Si)2种不同成分的锆合金在室温和385℃的拉伸性能,采用扫描电镜(SEM)分析了断口形貌,采用透射电镜(TEM)分析合金与第二相的微观结构。结果表明:各材料均有较好的力学性能,SZA4-450℃的强度最高,SZA4-560℃和SZA6-560℃的塑性最好;各材料的微观断口形貌均为韧窝,表明断裂方式为韧性断裂,同时可见大量的第二相粒子均匀、弥散地分布在基体中;SZA-4中存在2种密排六方结构(HCP)的第二相,尺寸较小的为Zr(Nb F20e Cr)2,尺寸较大的为Zr(Nb Fe Cr Ge)2,SZA-6中存在面心立方结构(FCC)的(Zr Nb)2 Fe和HCP结构的Zr(Nb Fe)2 2种第二相。最后分析了热处理工艺和合金成分对拉伸性能及显微组织的影响,认为热处理工艺的影响起主要作用。     

M5合金的堆内外性能概述

概述了法国法马通公司开发的新型燃料包壳材料 M5合金在堆内外的腐蚀、吸氢、显微组织、蠕变、辐照生长等性能。从已获得的堆内数据证明， M5合金包壳在抗腐蚀、吸氢、蠕变、辐照生长方面大大优于最佳化的 Zr- 4合金包壳。可以预计， M5新合金包壳能满足燃耗达 65GW· d· t－ 1的设计要求。在法马通推出的 PWR燃料组件 AFA- 3G已采用了 M5合金包壳。     

温度及氢化物对Zr-Sn-Nb合金焊缝疲劳裂纹扩展行为的影响研究

采用小尺寸三点弯曲试样完成了渗氢和未渗氢Zr-Sn-Nb合金母材和焊缝在室温和360 ℃下的疲劳裂纹扩展速率试验,研究了温度和氢化物对焊接薄板的疲劳裂纹扩展行为的影响。结果表明,腐蚀吸氢后,在母材和焊缝区均析出了呈水平向分布的片状氢化物。相比母材区,焊缝区析出的氢化物更为致密。在相同温度下,未渗氢母材的抗疲劳裂纹扩展性能均优于未渗氢焊缝。腐蚀吸氢后,母材在相同温度下的抗疲劳裂纹扩展性能也优于焊缝。在室温下,腐蚀吸氢后的母材和焊缝的抗疲劳裂纹扩展性能相比吸氢前明显下降。360 ℃下,渗氢母材和焊缝中的氢化物部分溶解,使得其抗疲劳裂纹扩展性能得到一定程度提升。     

新型高温锆合金在过热蒸汽中的腐蚀性能

研究了不同含量的Zr-Fe-Cr合金的显微组织及其在500℃,10.3 MPa 过热蒸汽中的耐腐蚀性能.结果表明,Zr-Fe-Cr合金经过真空熔炼、β淬火、真空包覆热轧和冷轧,以及真空退火处理得到的组织主要为α-Zr基体和弥散分布的Zr(Cr,Fe)2粒子.在500℃,10.3 MPa 过热水蒸汽中,含有少量合金元素的Zr-0.2Fe-0.1Cr和Zr-4合金会发生疖状腐蚀,而含有适当Fe、Cr的Zr-Fe-Cr合金为均匀腐蚀.Zr-1.0Fe-0.6Cr合金耐蚀性最好,其耐过热蒸汽腐蚀能力优于N18和Zr-4合金;含Fe、Cr元素不同的锆合金试样由于成分不同,耐腐蚀性能也有明显差别,说明调整合金成分是改善锆合金在500℃,10.3 MPa 过热蒸汽中耐腐蚀性能的主要途径.     

Transmission electron microscopy examination of oxide layers formed on Zr alloys

A transmission electron microscopy investigation was performed on oxides formed on three zirconium alloys (Zircaloy-4, ZIRLO and Zr-2.5Nb) in pure water and lithiated water environments. This research is part of a systematic study of oxide microstructures using various techniques to explain differences in corrosion rates of different zirconium alloys. In this work, cross-sectional transmission electron microscopy was used to determine the morphology of the oxide layers (grain size and shape, oxide phases, texture, cracks, and incorporation of precipitates). These characteristics were found to vary with the alloy chemistry, the corrosion environment, and the distance from the oxide/metal interface. These are discussed and used in conjunction with observations from other techniques to derive a mechanism of oxide growth in zirconium alloys.     

Microstructure and Corrosion Behavior about Zr-Cu-Cr Alloy

Seven kinds of Zr-Cu-Cr alloy samples were prepared by using crystalline zirconium as the base material, through normalized processing and annealing at 600 ℃/5 h. The corrosion tests were carried out in static autoclave with different water chemistry conditions, and the microstructures of alloys were studied by using EBSD, SEM and TEM to investigate the effects of Cu and Cr interaction on the microstructure and corrosion resistance of zirconium alloys. The results show that the addition of Cu element refines the recrystallized grains. When the Cr content is 1.0%, it has grains with a size of 40 μm or more. There are two kinds of second phases in Zr-Cu-Cr alloys. Zr₂Cu phase (bct) with a size of 100 nm or more and ZrCr₂ phase (hcp) with a size of 60 nm or less. As the content of Cu increases, the number of Zr₂Cu increases. As the content of Cr increases, the size of ZrCr₂ phase does not change obviously, but the number and distribution band density increase. When exposed to the superheated steam at 400 ℃/10.3 MPa, the corrosion resistance of Zr-0.3Cu-0.2Cr and Zr-0.3Cu-0.5Cr alloys is worse, the other alloys still don’t have corrosion transition after corroding 100 days, and the corrosion resistance is better. Zr-1.0Cr alloy has the best corrosion resistance. When exposed to the 360 ℃/18.6 MPa/0.01 mol/L LiOH aqueous solution for 42 days, all of alloys have poor corrosion resistance, and the addition of Cu element reduces their corrosion resistance.     

Zr-Cu-Cr合金的显微组织及腐蚀行为

以结晶锆为基材配制了7种Zr-Cu-Cr合金样品,经归一化加工及600 ℃/5 h退火处理,在不同水化学条件的静态高压釜中对所制得的Zr-Cu-Cr合金样品进行了腐蚀试验,并采用EBSD、SEM和TEM表征合金基体的显微组织,探究Cu和Cr交互作用对锆合金基体显微组织及耐腐蚀性能的影响。结果表明,添加Cu元素可细化合金再结晶晶粒,Cr含量为1.0%（质量分数）时,合金中出现40 μm以上的较大晶粒。Zr-Cu-Cr合金中存在2种第二相：100 nm以上的体心四方的Zr2Cu相和60 nm以下的密排六方的ZrCr₂相。Zr₂Cu相随Cu含量的增加而增多,ZrCr₂相随Cr含量的增加尺寸变化不明显,但数量及分布条带密度增加。在400 ℃/10.3 MPa过热蒸汽中,Zr-0.3Cu-0.2Cr和Zr-0.3Cu-0.5Cr合金耐腐蚀性能较差,其余合金腐蚀100 d后仍没有发生腐蚀转折,耐腐蚀性能较好,Zr-1.0Cr合金耐腐蚀性能最好。在360 ℃/18.6 MPa/0.01 mol/L LiOH水溶液中腐蚀42 d后,合金的耐腐蚀性能都很差,添加Cu元素会降低其耐腐蚀性能。     

The corrosion of some zirconium alloys under radiation in moist carbon dioxide-air mixtures

In-reactor experiments are reported in which Zircaloy-2 and $\text{Zr-2}\text{1}\text{2}$ wt % Nb alloys were exposed to moist carbon dioxide-air mixtures at 300°C for periods up to ≈ 800 days. For Zircaloy-2 the corrosion was significantly enhanced by the reactor radiation but the percentage hydrogen pick-up was reduced. For $\text{Zr-2}\text{1}\text{2}$ wt % Nb alloy the effect of radiation on the corrosion rate ranged from a slight suppression to a significant enhancement, depending on the metallurgical condition of the alloy, but there appeared to be no effect on the percentage hydrogen pick-up. The effect of improving the purity of the corrodent was also studied in the absence of radiation. The results are used to predict that the corrosion and hydrogen pick-up of typical reactor pressure tubes exposed to moist carbon dioxide-air mixtures are unlikely to cause a significant deterioration of their mechanical properties.     

低浓度硼对锆合金缓蚀作用研究

采用动电位极化和电化学阻抗谱法（EIS）研究了核电厂包壳材料锆合金在3种pH值相同的正常硼锂水质中的高温电化学腐蚀行为;采用高压釜腐蚀增重和微观分析等手段研究了锆合金在2种锂浓缩水质中的均匀腐蚀行为。高温电化学腐蚀试验表明:在3种pH值相同的正常硼锂水质中,随着硼浓度的增加, 锆合金的钝化电流密度减少而交流阻抗值增大,硼对减缓锆合金的腐蚀有利。均匀腐蚀试验表明:相对于无硼的锂浓缩水质而言,加硼显著降低了锆合金的腐蚀增重量,减少了氧化膜厚度,并使氧化膜更为致密,对提高锆合金的耐锂浓缩加速腐蚀有明显作用。      

Alloys based on niobium and their properties

Conclusions A number of refractory alloys based on niobium were developed, and their properties were investigated; the complex of these properties permits the recommendation of these alloys for use in various fields of technology. The alloys are characterized by good technological properties, ensuring the production of various objects: sheets, bars, tubes, and wires, under industrial conditions. The most heat-resistant alloys of the RN brand, possessing substantial short-term and long-term strength, are the alloys of tungsten, molybdenum, and zirconium (RN-6, RN-5). The alloys can be subjected to dispersion hardening.It was found that the alloy RN-6, produced by the method of centrifugal casting, possesses better mechanical properties than the alloys produced by arc and electron beam methods, as a result of its fine-grained structure. The alloying of niobium alloys with titanium, instead of zirconium, causes a smaller increase in the strength, especially at increased temperatures; however, their plasticity increases somewhat. Alloys of the RN type possess high corrosion resistance in lithium at 1000°C, as well as in solutions of hydrochloric and sulfuric acids.Translated from Atomnaya Énergiya, Vol. 23, No. 1, pp. 32–37, July, 1967.     

Systematic approach to predicting corrosion of zirconium alloys in the water coolant of nuclear reactors

A method of semiempirical prediction of corrosion of cladding zirconium alloys as a function of the operating conditions and composition is presented. The laws of thermodynamics and chemical kinetics of the oxidation reactions of a multicomponent zirconium alloy form the physicochemical basis of the computational method. The method is based on a model developed at the All-Russia Research and Design Institute of Integrated Power Technology for the corrosion of commercial and experimental zirconium alloys in water media under autoclave and reactor conditions taking account of the composition of the alloy and the water chemistry. The model is verified on the basis of independent tests performed on a series of zirconium alloys under autoclave and reactor conditions. The method developed makes it possible to predict the corrosion of fuel-element cladding made from zirconium alloys with fuel burnup to 80 MW·days/kg under the conditions of one- and two-phase VVER and RBMK coolant.     

Effects of Fe and Cr on corrosion behavior of ZrFeCr alloys in 500 °C steam

A study of the corrosion behaviors of ZrFeCr alloy and the influence of microstructure on corrosion resistance are described by X-ray diffraction and scanning electron microscope in this paper. The results show that several ZrFeCr alloys exhibit protective behavior throughout the test and oxide growth is stable and protective. The best alloy has the composition Zr1.0Fe0.6Cr. Fitting of the weight gain curves for the protective oxide alloys in the region of protective behavior, it showed nearly cubic behavior for the most protective alloys. The Zr1.0Fe0.6Cr has the more laves Zr(Fe,Cr)₂ precipitate in matrix and it has the better corrosion resistance. The Zr0.2Fe0.1Cr has little precipitate, the biggest hydrogen absorption and the worst corrosion resistance. The number of precipitates and the amount of hydrogen absorption in Zr alloy plays an important role on corrosion resistance behaviors in 500 °C/10.3 MPa steam.     

钒合金的氢脆机理研究

利用气相渗氢法，测试了几种钒合金在氢含量最高达到113mg/kg范围内的拉伸性能变化。实验结果表明：低强度的钒合金具有较好的抗氢脆性能。合金中的氧会加重钒合金（特别是强度较高者）的氢脆敏感性。机理分析揭示钒合金的氢脆断裂主要由沿晶断造成，氧和合金强度的影响均是通过改变合金的晶界与晶粒的对比强度来实现的。