Potentialities of Mössbauer Spectroscopy for Studying Zirconium Alloys and Their Oxide Films

A brief review and an analysis of results of a study of iron- and tin-bearing zirconium alloys and their oxide films by the method of Mössbauer spectroscopy (MS) are presented. The potentialities of MS for studying the phase composition of zirconium alloys are described and the changes in the states of iron and tin atoms are presented as a function of additional alloying and thermomechanical treatment. The conditions of formation of Zr₂Fe and Zr₃Fe intermetallic compounds and chromium- and niobium-bearing compounds are considered. It is shown that some intermetallic compounds transform into other compounds at room temperature. Metallic iron and tin are shown to be present in oxide films of zirconium alloys, and their concentration is shown to affect the corrosion resistance of zirconium alloys.     

System Zirconium-Nitrogen

Iodide zirconium was combined with calculated amounts of nitrided zirconium sponge and arc melted to prepare alloys in the 0 to 6 wt pet N region. Annealing treatments were carried out at 21 temperature levels. Metallographic examination of the heat-treated specimens permitted construction of the binary phase diagram from 0 to 6 pet N. Features of the diagram include the peritectic formation of both a and β solid solutions. The maximum solubility of nitrogen is 0.8 pet in β zirconium and 4.8 pet in a zirconium. An X-ray study of nitrided materials was made in the range 6 to 13 wt pet N region because serious nitrogen losses were experienced when attempts were made to arc melt these high nitrogen alloys.     

Influence of minor additions on the emissivity of the oxide scale of FeCrAlY alloys during resistance heating

Chromium aluminum yttrium (FeCrAlY) alloys owe their low oxidation rate to the formation of a slow growing α‐alumina scale. For material used for heating elements not only the life time and the behavior of the resistance during the life time is of relevance, but also the emission coefficient of the oxide scale. The power density J_S produced by resistance heating of strip with 50 µm thickness and about 5–6 mm width at 1050 °C is approximately equal to the radiant flux density, which is according to Stefan–Boltzmann's law proportional to the total emission coefficient ε_g. Resistance heating tests were performed on samples made from FeCrAlY alloys with different zirconium and carbon content. The “high zirconium” containing FeCrAlY alloys (zirconium > about 0.10%) have a higher power density/emissivity than the “low zirconium” alloys. In parallel with this, all samples with higher power density/emissivity have internal oxidation and therefore a “rough” metal–oxide interface. Thus, one cause for the increase of the emissivity of the scale could be this rough metal–oxide interface; other causes could be a higher amount of zirconium incorporated into the scale, more pores and/or different grain structure in the scale. Additionally the carbon content influences the appearance of a higher emissivity and the internal oxidation.     

SPD技术对锆及锆合金力学行为影响研究现状

综述了锆及锆合金剧烈塑性变形(SPD)后性能变化的研究进展,系统阐述了锆及锆合金经剧烈塑性变形后显微硬度、拉伸/压缩性能、高低周疲劳性能,重点介绍了SPD技术在纯锆、Zr-Nb系合金中的应用。经过剧烈塑性变形后,锆及锆合金的抗拉强度及屈服强度均显著提升,但依据剧烈塑性成形轨迹、合金成分、第二相分布、热处理制度不同,其提升程度存在一定的差别。位错滑移是锆及锆合金高周疲劳的主要损伤机制,位错运动(包括位错滑移及位错攀移)是锆及锆合金低周疲劳的主要损伤机制。文章最后指出现阶段锆及锆合金SPD技术的发展趋势及应用前景。     

Corrosion behavior of Zr–Nb–Cr cladding alloys

Zr-Nb-Cr alloys were used to evaluate the effects of alloying elements Nb and Cr on corrosion behavior of zirconium alloys. The microstructures of both Zr substrates and oxide films formed on zirconium alloys were characterized. Corrosion tests reveal that the corro- sion resistance of ZrxNb0.1Cr （x = 0.2, 0.5, 0.8, 1.1; wt%） alloys is first improved and then decreased with the increase of the Nb content. The best corrosion resistance can be obtained when the Nb concentration in the Zr matrix is nearly at the equilibrium solution, which is closely responsible for the formation of columnar oxide grains with protective characteristics. The Cr addition degrades the corrosion resistance of the Zrl.lNb alloy, which is ascribed to Zr（Cr,Fe,Nb）2 precipitates with a much larger size than β-Nb.     

Untersuchungen über das Korrosionsverhalten von Zirkoniumlegierungen. III. Untersuchungen an Zirkonium-Titan-Legierungen

Investigations into the corrosion behaviour of zirconium alloys III. Investigations on zirconium titanium alloys Investigations on zirconium alloys containing up to 4OO% titanium and, eventually, up to 10% Nb or Mo and small amounts of Fe, Ni and Cr (together 1.5% maximum) have revealed that titanium increases the dissolution power of zirconium for other alloying elements without tending to form two-phase structures. As to corrosion behaviour the better alloys are somewhat superior to other alloys. While titanium impairs the corrosion resistance of pure zirconium with respect to boiling mineral acids (20% HCl, sulphuric or nitric acids) titanium additions up to 10% of improve the corrosion behaviour of ZrNb and ZrMo alloys; alloys of the type Zr10Nb10Ti or Zr10Ti10Ta are comparable, with respect to the corrosion resistance, to pure zirconium. The scaling resistance of zirconium passes through a minimum at a five to ten percent Ti and arrives at its maximum value with 40% Ti. Further improvements may be obtained by addition of 10% Nb.     

Tetragonal phase stability in ZrO2 film formed on zirconium alloys and its effects on corrosion resistance

A thermodynamic model is developed to understand the origin of variation in the microstructure of ZrO₂ film formed on zirconium alloys and its effects on corrosion resistance. The correlation among the tetragonal phase fraction, the stress (macroscopic and internal one), the ZrO₂ grain size and the microstructural change of oxide film is formulized, and then analyzed. The results show that many complicated factors simultaneously govern the microstructure of oxide film. The tetragonal phase content near the oxide/metal interface, the macroscopic compressive stress near the interface, the decline gradient of macroscopic compressive stress and the internal stress induced by the transformation from the tetragonal to the monoclinic phase have very important influences on the transition from columnar grains to equiaxed grains, the crack formation and the degradation of oxidation resistance. The presence of intermetallic precipitates in oxide film may effectively relax the internal stress caused by transformation strain, stabilize the columnar-grain structure and reduce the probability of crack formation. How to reduce the transformation stress in the oxide film is a key to improve the corrosion resistance of zirconium alloys.     

含Nb锆合金第二相及其与腐蚀行为关系研究进展

含Nb锆合金具有优异的耐腐蚀性能、良好的机械性能和加工变形能力,是目前锆合金研究的重点。本文综述了近年来含Nb锆合金的研究现状,包括化学成分、变形及热处理工艺对第二相粒子析出的影响,介绍了锆合金腐蚀理论的研究进展,讨论了研究中存在的若干问题,为含Nb锆合金组织控制和耐腐蚀性能改善提供参考。     

与我国核电发展相关的堆芯关键材料——锆合金国产化问题

评述了我国“十五”期间在堆芯关键结构材料——锆合金的研发与产业化方面的最新进展。说明我国在改进Zr-4和新一代锆合金研究方面取得了明显的突破，材料研究已达国际先进水平；同时进一步完善了2条包壳管材生产线，为我国核电用包壳管的国产化生产提供了基础保障。结合我国核电发展的实际情况，提出了我国要加快建设海绵锆生产厂，建立格架用条带生产线，完善管、板材开坯设备等建议，并指出锆铪分离技术、条带制造方面的织构控制及在线检测技术是需解决的关键技术。文章强调，高燃耗组件用新一代锆合金的研发仍是科研的主要任务。     

Die Oxydation von intermetallischen Zirkoniumlegierungen in Sauerstoff und Wasserdampf bei 400 °C

The oxidation of intermetallic zirconium alloys in oxygen and steam at 400°C The author has studied the oxidation behaviour of some intermetallic zirconium alloys in oxygen and steam. Depending on their behaviour the alloys can be divided into three categories:

• 1 Selective oxidation of alloying elements in the case of the alloys ZrAl₃ et ZrSi
• 2 Selective oxidation of Zr produced by rearrangement and enrichment of alloying elements in the case of Zr₄Sn, ZrCU₃ ZrNi, ZrV₂ and ZrMo_2/
• 3 Oxidation control by mixed oxides in the case of ZrNb and ZrTa

The mechanism of the corrosion of ZrAl₃ and ZrSi₂ in steam is interpreted in terms of the selective attack of Al and Si respectively.     

Zirconium-Niobium Alloys for Core Elements of Pressurized Water Reactors

The main characteristics of niobium-bearing zirconium alloys used for fabricating fuel element claddings of pressurized water reactors are considered. It is shown that the high corrosion and radiation resistance of zirconium parts is provided by the chemical composition, structure, and phase composition of the alloys. The Zr – Nb alloys developed in Russia provide reliable operation of fuel elements and fuel rod arrays in active reactors and serve as a basis for new modifications.     

Zr-4合金表面氧化膜的电化学阻抗谱特征

电化学阻抗谱是分析锆合金表面氧化膜结构及其演化行为的有效方法。利用10%HCl溶液研究了锆合金在400 ℃, 10.3 MPa过热蒸汽中腐蚀后的表面氧化膜电化学阻抗行为。结果表明：锆合金过热蒸汽腐蚀初期表面氧化膜的阻抗谱为单一容抗弧,随着腐蚀进行而演变为双容抗弧。氧化膜表现为双层膜结构特征。氧化膜阻挡作用的降低是锆合金过热蒸汽腐蚀发生转折的一个原因。锆合金中第二相粒子对氧化膜阻抗谱及合金耐蚀性有较大影响     

Effect of Zirconium on Magnesium-Thorium and Magnesium-Thorium-Cerium Alloys

Data are presented in this paper to show that addition of zirconium to sand-cast Mg-Th alloys effects a marked decrease in the grain size of these alloys which is accompanied by a significant increase in the mechanical properties over the entire range of thorium content investigated. The beneficial effect of zirconium on the strength properties is maintained at elevated temperatures up to 700°F. In addition the alloys exhibit exceptionally high creep resistance at temperatures up to 600°F. Zirconium does not greatly improve the strength or creep characteristics of extruded Mg-Th alloys. Cerium is not a desirable addition to Mg-Th-Zr alloys.     

核电锆管的表面改性技术

锆合金已被广泛用于核反应堆的堆芯结构材料,但其耐腐蚀性能和耐磨性能制约着使用寿命,采用合适的表面处理技术可以改善其表面完整性.通过对近几年核用锆合金表面处理的研究进行归纳总结,简单介绍了锆合金的研发进展,并着重对能提高锆合金耐腐蚀性能和耐磨性能的表面处理技术进行了综述,如喷丸处理、超声冲击强化、冷轧、渗氮和渗铝等.总结了各种表面处理技术对锆合金的微观结构和性能的影响,并介绍了结构和性能之间的联系.最后对锆合金表面处理技术进行了讨论和展望.     

Evidence for direct liquid to alpha transformation in zirconium alloys

The possibility of solidification of unalloyed zirconium and zirconium–niobium alloys from the liquid phase directly into the low temperature α phase is examined and the role played by solidification microstructure in modifying the β to α′ martensitic transformation in rapidly solidified zirconium and zirconium–niobium alloys is discussed.     

Untersuchung über das Korrosionsverhalten von Zirkoniumlegierungen. IV. Das Lochfraßverhalten Zirkoniumlegierungen

Investigation into corrosion behaviour of zirconium alloys. IV-Pitting behaviour of zirconium alloys Electrochemical investigations into the resistance of a number of Zr-alloys in different solutions against pitting corrosion have shown that additions of Va- and VIa-group metals and in particular Ti improve the resistance of pure Zr. Metals forming local elements decrease pitting corrosion resistance. Minor amounts of Fe, Ni and Cr have practically no influence. The pitting corrosion resistance of Zr and its alloys decreases with increasing concentration of chloride ions in the solutions. Additions of SO₄-ions retard the beginning of the pitting but do not shift the pitting corrosion potential. NO₃-ions on the other hand produce a real inhibition. Newly developed methods for the quick determination of the pitting corrosion potential were very useful for the described investigations.     

锆微弧氧化表面处理技术研究进展

锆及锆合金是重要的核结构材料和有潜力的生物医用材料,但在实际应用中,腐蚀、磨损易造成其失效,而适当的表面改性是提高它们服役性能的有效手段。重点介绍了锆及锆合金微弧氧化（MAO）表面处理技术的研究现状,讨论微弧氧化过程中电压电流特征及微弧放电机理,总结电解液体系及电参数对锆微弧氧化膜生长及膜层性能的影响规律,最后指出目前存在的问题和后续的研究方向。锆微弧氧化膜硬度高,致密性好,能大幅度提升基材的抗磨损和抗腐蚀性能。因此,锆微弧氧化技术在核电及生物医学领域有着很好的应用前景。此外,电解液中铝、硅元素进入微弧氧化膜后可以稳定膜层中高温氧化锆相（t-ZrO2）,避免膜层中应力集中和微裂纹的产生。用P和Ca元素修饰后的锆微弧氧化膜具有较好的生物活性、抗体液腐蚀和抗菌性能。     

Repassivation kinetics of zirconium alloys investigated by a scratching electrode technique

The repassivation behavior of zirconium alloys in a solution containing 0.1 M H₃BO₃ and 0.1 M LiOH was examined by means of a rapid scratching electrode technique. The repassivation behavior of the scratched surface of the alloys varied with time. The place exchange model reveals that at the initial stage of repassivation (within 10 ms) log i (t) is linearly proportional to q (t) with a slope of 1/K. The high field ion conduction model reveals that after 25 ms log i (t) is linearly proportional to 1/q(t) with a slope of cBV. The cBV value, in particular, which is a measure of the protectiveness and erosion resistance of an alloy, increases when there is an increase in the Nb content of the alloys, as well as in the applied potential and the solution temperature. This result suggests that these parameters can affect the repassivation rate of zirconium alloy.     

Determination of Oxygen Diffusion Along Nickel/Zirconia Phase Boundaries by Internal Oxidation

Internal oxidation tests with nickel alloys that contained up to 8 at.% zirconium were carried out. All alloys were two-phase consisting of γ-Ni and the intermetallic phase Ni₅Zr. Their behavior under low oxygen partial pressures in the range of 800–1,000?°C could not be described by the Wagnerian analysis. Oxygen diffusivity along the interface nickel/monoclinic zirconia plays an important role for the rate of internal oxidation. The early stages of internal oxidation show the in situ mode where diffusion of the less noble element zirconium cannot diffuse in the matrix and is oxidized instantly. Later in the process the mode shifts from in situ towards the diffusive mode as zirconium has the possibility to diffuse. This change could also be observed as the size of the oxide particles varied with ongoing oxidation. A method for the determination of the oxygen diffusivity in nickel/monoclinic zirconia phase boundaries is presented.     

利用SRIM分析辐照对碳化物和氧化物陶瓷的影响

弥散强化在改善合金性能方面发挥着重要作用,而碳化物和氧化物陶瓷作为常用的弥散强化颗粒,其稳定性对于应用于恶劣环境的核反应堆中的合金非常重要,因此研究SiC、TiC、ZrC、Al₂O₃、Y₂O₃ 和 ZrO₂的抗辐射性具有重要意义。利用 SRIM 程序模拟了不同能量、不同类型的入射离子对不同材料的影响,分析了不同辐照剂量下氧化锆的辐照损伤。结果表明,随着入射离子能量的增加,入射离子在靶材中的分布趋于均匀,入射离子的停止位置和靶材的损伤深度有所增加。入射离子的种类不同,对靶材的损伤程度也大不相同,不利于对比材料的抗辐射能力。在相同的辐照条件下,入射离子的分布随辐照剂量的增加保持不变,但辐照损伤会不断累积直至饱和。在6种物质中,氧化锆和碳化锆的抗辐射性能较好。对氧化锆增强的钨合金在700 ℃进行碳离子辐照实验,发现氧化锆具有良好的辐照性能。