Zr-4合金α-Zr固溶体中的Fe、Cr含量分析

将电化学分离Zr-4合金中Zr(Fe,Cr)2第二相粒子的技术和原子吸收光谱分析技术相结合，建立了一种分析Zr-4合金α-Zr固溶体中Fe,Cr含量的新方法，并用这种新方法分析了不同热处理状态下Zr-4合金α-Zr固溶体中的Fe,Cr含量。分析结果表明，随着淬火温度的增加。α-Zr固溶体中的Fe,Cr含量和Fe/Cr比值均增加，而Zr(Fe,Cr)2第二相粒子中的Fe/Cr比值则相应降低。结合以前的工作，可得结论：过饱和固溶在α-Zr固溶体中的Fe,Cr含量对Zr-4合金的耐水侧腐蚀性能有重要影响。     

Zr-4合金α-Zr固溶体中Fe,Cr含量的研究

将电化学分离Zr-4合金中Zr(Fe,Cr)2第二相粒子的技术和原子吸收光谱分析技术相结合,建立了一种分析Zr-4合金α-zr固溶体中Fe和Cr含量的新方法,并用这种新方法分析了不同热处理状态下Zr-4合金α-zr固溶体中的Fe和Cr含量。分析结果表明,随着淬火温度的增加, α-zr固溶体中的Fe,Cr含量和Fe/Cr比值均增加,而Zr(Fe,Cr,)2第二相粒子中的Fe/Cr比值则相应降低,并且在淬火状态,α-zr固溶体中Fe,Cr的含量均大于其最大饱和固溶度。结合以前在高温水、蒸汽中的腐蚀试验结果发现,α-zr固溶体中的Fe,Cr含量对Zr-4合金的耐水侧腐蚀性能起着重要作用,并且,过饱和固溶在α-zr中的Fe,Cr含量存在一临界值,当Fe和Cr含量大于临界值时,Zr-4合金就具备抗疖状腐蚀的能力。     

Zr-4合金基体中Fe,Cr含量的间接测量(英文)

应用定量金相和理论计算发展了分析 Zr-4 合金α-Zr 基体中Fe,Cr 含量的方法。结果表明,只要能精确测量出 Zr-4 合金中第二相所占的体积分数,则计算出的基体中 Fe,Cr 含量就更准确。在分析的三种不同热处理工艺的 Zr-4 样品种中,具有不同的 Zr(Fe,Cr)2 第二相粒子份额以及不同的基体 Fe,Cr 含量,但其第二相大小相近。此外,基体中 Fe,Cr 含量高的试样具有较好的抗疖状腐蚀能力,认为影响 Zr-4 合金腐蚀行为的主要因素是基体中的 Fe,Cr 固溶体含量,而不是第二相粒子大小。     

Zr（Fe,Cr）2金属间化合物的氧化

用非自耗电弧炉熔炼了比值(重量比值)不同的Zr(Fe,Cr)_2,并在773K和973K的空气中氧化。经X射线衍射和电子衍射分析表明:当Fe/Cr≤4.5时,Zr(Fe,Cr)_2,是MgZn_2型(六方)的Laves相,它的晶格常数随Fe/Cr比增加而收缩。Zr(Fe,Cr)_2氧化后生成的稳定氧化物是单斜ZrO_2和六方(Fe,Cr)_2O_3。在形成稳定氧化物之前,还会出现亚稳定的立方ZrO_2。根据本实验结果讨论了Zr-4合金中Zr(Fe,Cr)_2第二相对腐蚀性能的影响。     

Zr—4合金中第二相的研究

应用透射电子显微镜研究了Zr-4合金经各种热处理后的微观结构,确定了第二相的晶体结构。经β相固溶处理后,板条α-Zr晶界上析出的第二相为C_(15)型Zr(Fe、Cr)_2Laves相,重新在α相区不同温度加热后存在C_(15)型私C_(14)型两种结构的Zr(Fe、Cr)_2Laves相。此外,本文对Zr-4合金中第二相的种类进行了讨论。     

热处理对锆-4合金中第二相结构和成分的影响(英文)

用电化学方法分离出锆-4合金中第二相,研究了不同热处理制度对第二相结构和成分的影响。锆-4合金经1050℃β相加热空冷后,析出的第二相为立方结构的Zr(Fe,Cr)_2,Fe/Cr比值在2.1～2.5之间。试样重新在600～800℃下加热3h,晶体结构不发生改变,只是Fe/Cr比值逐渐降至1.9;但在700～800℃下加热后,有少量的六方结构Zr(Fe,Cr)_2第二相析出。生产厂提供的锆-4板中第二相是六方结构的Zr(Fe,Cr)_2,重新在700～800℃加热3h,晶体结构不发生变化,Fe/Cr比值由1.9降至1.5左右。这说明在重新加热时,第二相中的Fe和Cr与周围基体中的Fe和Cr会相互扩散置换。试样从β相冷却析出第二相时,Fe原子的扩散比Cr原子快;Cr原子在六方晶格Zr(Fe,Cr)_2中的固溶度比在立方晶格Zr(Fe,Cr)_2中的大。由于这些原因造成了第二相成分随热处理制度不同而变化的现象。     

热加工对Zr-Sn-Nb合金显微组织的影响研究

对Zr-Sn-Nb合金在4种温度(750℃、780℃、800℃和820℃)下进行了热／冷加工和最终再结晶退火,并对在上述4种温度下加热的试样进行了淬火处理。用透射电子显微镜(TEM)和光学金相显微镜(OM)研究了试样的显微组织、β-Zr以及第二相粒子的特征：结果表明,当加热温度达到780℃或高于此温度时．Zr-Sn-Nb合金已进入α-β双相区;随着加热温度的增加,β-Zr相含量增多;加工后试样中的第二相粒子大部分为C14型六方结构的Zr(Fe、Cr)2Laves相,与Zr-4合金中第二相结构相同,点阵常数α=0．502nm、c=0．818nm。同时．还发现有少量C15型面心立方结构Zr(Fe,Cr)2Laves相,点阵常数α=0．716nm．     

热处理对锆-4合金中第二相结构和成分的影响

用电化学方法分离出锆-4合金中第二相,研究了不同热处理制度对第二相结构和成分的影响。锆-4合金经1050℃β相加热空冷后,析出的第二相为立方结构的Zr(Fe,Cr)_2,Fe/Cr比值在2.1～2.5之间。试样重新在600～800℃下加热3h,晶体结构不发生改变,只是Fe/Cr比值逐渐降至1.9;但在700～800℃下加热后,有少量的六方结构Zr(Fe,Cr)_2第     

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。     

Zr(Fe,Cr)_2金属间化合物在500℃过热蒸汽中的腐蚀(英文)

用非自耗电弧炉熔炼了Fe/Cr比值为1.75和4.50的Zr(Fe,Cr)_2金属间化合物,它们的粉末经500℃、10.3MPa过热蒸汽腐蚀不同时间后,用X射线衍射、电子探针和透射电子显微镜分析了腐蚀后生成物的结构及其形貌,以及成分的重新分布。Fe/Cr比值不同的Zr(Fe,Cr)_2腐蚀后的生成物都相同,但是含Cr高的更不易被腐蚀。腐蚀初期的生成物是立方ZrO_2,并析出α-Fe(Cr),在继续腐蚀时,立方ZrO_2逐渐转变为单斜ZrO_2,α-Fe(Cr)也逐渐被氧化成(Fe,Cr)_3O_4。Fe和Cr在偏聚时,Fe原子的扩散速率比Cr原子快。根据实验结果,讨论了第二相影响Zr-4合金腐蚀性能的原因。     

The Effect of Oxide Microstructure on Kinetic Transition in Out-of-pile Steam Corrosion Test for Zircaloy-2 and Nb-added Zircaloy-2

In order to study the mechanism of kinetic transition of corrosion rate for zirconium alloys, oxide films formed on Zircaloy-2 (Zry-2) and Nb-added Zircaloy-2 (0.5Nb/Zry-2) in steam at 673 K and 10.3 MPa were examined with TEM and SIMS.

Kinetic transition occurred at almost the same oxide thicknesses for both Zry-2 and 0.5Nb/Zry-2, but the corrosion rate after the transitions were quite different for the two alloys. Zircaloy-2 showed cyclical oxidation, while the weight gain of 0.5Nb/Zry-2 increased linearly.

The morphology and crystal structure were similar for the oxides of the two alloys and both the oxide films still mainly consisted of columnar grains even after the transition. Interface layers which mainly consisted of a-Zr crystallites were observed for both alloys and the oxygen content in the interface layers increased after the transition.

The solute concentrations of Fe, Cr and Ni became higher, accompanying the increase of oxygen concentrations at columnar grain boundaries in the oxide films after the transition for 0.5Nb/Zry-2. It was thought that the properties of grain boundaries of the 0.5Nb/Zry-2 oxide films changed after the transition, and the increase in oxygen diffusivity at grain boundaries caused the linear increase in weight gain.     

The effect of alloying modifications on hydrogen uptake of zirconium-alloy welding specimens during corrosion tests

The hydrogen uptake behavior during corrosion tests for electron beam welding specimens made out of Zircaloy-4 and zirconium alloys with different compositions was investigated. Results showed that the hydrogen uptake in the specimens after corrosion tests increased with increasing Cr content in the molten zone. This indicated that Cr element significantly affected the hydrogen uptake behavior. Fe and Cr have a low solubility in α-Zr and exist mainly in the form of Zr(Fe,Cr)₂ precipitates, which is extremely reactive with hydrogen in its metallic state. It is concluded that the presence of Zr(Fe,Cr)₂ second phase particles (SPPs) is responsible for the increase in the amount of hydrogen uptake in the molten zone of the welding samples after corrosion, as Zr(Fe,Cr)₂ SPPs embedded in α-Zr matrix and exposed at the metal/oxide interface could act as a preferred path for hydrogen uptake.     

Irradiation Effects on Corrosion Resistance and Microstructure of Zircaloy-4

In order to investigate irradiation effects on nodular corrosion resistance of Zircaloy-4, an out-of-pile corrosion test was conducted using Zircaloy-4 specimens cut from the channel box of a fuel assembly irradiated in the BWR (Monticello reactor) up to the neutron fluence of 1.53×10²⁶ n/m² (E>1MeV). The corrosion test was carried out in high pressure steam of 10.3 MPa at 783 K for 24 h. No nodules appeared on the specimens cut from welded areas of the channel box and nodular corrosion resistance tended to be better with increasing neutron fluence. Microstructural evolution in the form of irradiation-induced release of Fe atoms from Zr(Fe, Cr)2 type precipitates was detected by an analytical electron microscope. It was found that the higher the concentration of dissolved Fe and Cr in the grains of Zircaloy-4, the better the nodular corrosion resistance.     

加工工艺对Zr—4管抗疖状腐蚀的影响

应用高压釜，金相及电子显微镜等研究了不同加工工艺的Ｚｒ－４包壳的疖状腐蚀行为。结果表明，改进工艺加工的管材比常规工艺加工的管材有更优良的抗疖状腐蚀性能，去应力试样比再结晶试样有较强的抗疖状腐蚀能力，影响Ｚｒ－４合金抗腐蚀性能的主要因素是Ｆｅ和Ｃｒ合金元素在α－Ｚｒ中的固溶含量，而不是第二相粒子的大小。     

Out-of-pile and In-pile Perfomance of Advanded Zirconium Alloys (HANA) for High Burn-up Fuel

The performance of the advanced Zr alloys (HANA) for a high burn-up fuel has been evaluated in the out-of-pile and in-pile conditions. The corrosion resistance of the HANA claddings was superior to Zicaloy-4 in a PWR-simulating loop condition. The improved corrosion resistance of the HANA claddings was attributed to the fine distribution of the precipitate. HANA claddings showed a higher creep resistance as compared to Zircaloy-4 from the thermal creep test. The deformation behavior of HANA in a LOCA condition was similar to Zircaloy-4. Threshold ECR value of HANA was higher than the conventional value of 17% in Zircaloy-4, which is mainly due to the fact that the Nb decreases the oxidation rate as well as the hydrogen pickup. Fretting wear test revealed that HANA claddings have a similar wear resistance to Zircaloy-4. From the irradiation test up to burn-up of about 12 GWd/MtU, HANA claddings showed a better corrosion resistance as well as a better creep resistance than Zircaloy-4. The in-pile corrosion resistance of the HANA claddings was improved by 40–50% as compared to Zircaloy-4 on the basis of the oxide thickness measurements.     

Influence of second phase particles on corrosion resistance of N36 alloy in superheated steam

The nodular corrosion resistance of N36 (Zr–0.8Sn–1Nb–0.3Fe–0.12O, wt%) alloy with different temperatures of interstage annealing and optimized Zircaloy-4 (lower content of tin) cladding tubes were tested in 500 °C and 10.3 MPa superheated steam. The result showed that no nodular spots appeared on surface of N36 alloy cladding tubes after 500 h corrosion, while nodular spots on optimized Zircaloy-4 tubes after 8 h. The differences of weight gain between two kinds of N36 tubes suggested that the percentage (volume fraction) of tetragonal Zr dioxide in oxide film can be effectively influenced by characteristics, such as size, of the second phase particles on the oxide film-matrix boundary. The analysis by SEM and LRS clearly indicated that smaller and fine distributed second phase particles were beneficial to stabilize the oxide via endure the uniform stress so it could slow down the altering process from tetragonal Zr dioxide to monoclinic Zr dioxide.     

Zr-4合金在 LiOH水溶液中腐蚀机理的概述

综述了近十几年国内外对Zr-4合金在LiOH水溶液中腐蚀的研究,着重讨论了在LiOH水溶液中加速腐蚀的规律和机理,并分析了目前解释这种腐蚀机理的各种假说中存在的问题。     

Effect of additives on the susceptibility of zirconium alloys to nodular corrosion

A new approach based on a stability analysis of a uniformly growing oxide film was applied to estimate the effect of alloying additives on the susceptibility of zirconium alloys to nodular corrosion. The analytical results agree with available experimental data on effect of Fe and Ni on resistance of Zircaloy-2 and Zircaloy-4 to the growth of nodular oxide.     

Irradiated Behavior at High Burnup for HiFi Alloy

Irradiation tests of a BWR advanced Zr alloy (HiFi alloy) and Zircaloy-2 (Zry-2) were carried out in a Japanese commercial reactor and the irradiation performances of the materials were investigated. HiFi alloy and Zry-2 showed excellent resistance to corrosion up to 70 GWd/t, and furthermore, HiFi kept lower hydrogen pickup compared with Zry-2. TEM observation showed that the Fe/(Fe+Cr) ratio of Zr(Fe,Cr)2 type second phase particles (SPPs) for HiFi alloy and Zry-2 tended to decrease as fast neutron fluence increased and to saturate at high fluence. Zr-Fe-Cr SPPs did not completely disappear even for 6 cycles for the irradiated HiFi alloy and Zry-2. In order to clarify the mechanism of hydrogen absorption, an electrochemical technique was used for the oxide film of both materials as part of the out-of-pile test. The relation between the oxide surface potential and the hydrogen pickup fraction was estimated suggesting that the potential difference over the oxide film suppressed hydrogen (proton) diffusion in the oxide film.