Inconel 617合金中第二相的析出规律研究

利用SEM和TEM对Inconel 617合金在700℃时效0～1 000 h后的M_(23)C_6碳化物和γ′-Ni_3(Ti,Al)相的析出规律及第二相析出对硬度的影响进行了研究。结果表明,700℃时效过程中样品在160 h时达到硬度峰值,且硬度的提高与晶界处析出的不规则M_(23)C_6碳化物、晶粒内部析出的棒状M_(23)C_6碳化物和球状γ′相有关,其中γ′相对材料的强化效果更明显。时效初期,第二相以M_(23)C_6碳化物为主,γ′相倾向在碳化物周围的富Al和Ti的区域形核长大。两种相互依附的析出相存在共格取向关系,限制彼此的生长。γ′相数量不断增多并向碳化物内部生长,导致碳化物逐渐分解。时效后期,晶粒内部的碳化物几乎消失,晶粒内部弥散分布着大量球状γ′相。根据实验结果,讨论了两种析出相的析出长大规律。     

掺杂Cr2O3对UO2芯块烧结行为的影响

提高燃料燃耗的一个有效手段是通过增大UO₂晶粒尺寸来减少元件内部气体压力,在大晶粒UO₂芯块中,裂变气体到达晶界表面的距离增加,因而裂变气体的释放速率降低,元件内部气体压力的增高缓慢。本文研究了添加Cr₂O₃对UO₂晶粒尺寸的影响。对纯UO₂、添加0.5% Cr₂O₃及5% Cr₂O₃ 3种配方的芯块进行了试验,在5%H₂Ar保护下,以10 ℃/min和5 ℃/min的升温速率升温至1 700 ℃,然后烧结2 h或4 h,对比纯UO₂芯块与添加Cr₂O₃的芯块发现,添加Cr₂O₃可有效增大晶粒尺寸;较长的烧结时间可促进晶粒长大;较低的升温速率也使晶粒长大。烧结过程产生液相烧结,液相浸润晶粒边界,促进晶粒长大。     

阻氚用Fe-Al渗铝层表面稳态相Al2O3膜生长机理研究

为阐释Fe-Al渗铝层表面暂态相Al₂O₃膜向稳态相α-Al₂O₃膜的转变机理,探索稳态相α-Al₂O₃膜制备的氧化工艺参数范围,采用掠入射角X射线衍射仪、辉光放电光谱仪、聚焦离子束、透射电镜等,结合热重分析对CLAM钢基体Fe-Al渗铝层在940～980 ℃、1 Pa～20 kPa参数下的氧化生长行为进行了深入表征与机理分析。研究结果表明,在1 Pa～20 kPa氧分压范围内Al₂O₃膜生长初期反应速率常数随着氧分压的升高而增大,而后期反应速率常数反而随之下降;采用掠入射角X射线衍射仪对3～180 min氧化不同时期表面Al₂O₃膜的相结构进行了掠入射角分析,推测Al2O3膜的生长经历了从氧化初期形成暂态相γ-Al₂O₃（15 min）→过渡态相α-（Al_0.948Cr_0.052）₂O₃（30 min）→稳态相α-Al₂O₃（120～180 min）的演变过程,最短相转变时间约60～90 min,连续Al₂O₃膜厚度约2 000 nm;同时,结合聚焦离子束对30、120 min形成的Al₂O₃膜表面进行了精确定向切割制样,并采用透射电镜选区电子衍射分析验证了相转变前Al₂O₃膜结构为过渡态相α-（Al_0.948Cr_0.052）₂O₃（113）,转变后为稳态相α-Al₂O₃（113）,证实了Cr作为第三组元促进暂态相向稳态相α-Al₂O₃的转变规律。     

热老化对20Cr25NiNb不锈钢冲击韧性的影响研究

针对长时间高温下合金力学性能退化问题，开展超临界气冷堆候选包壳材料的热老化研究。对改进型气冷堆用原型20Cr25NiNb不锈钢和添加不同元素的改进型合金，开展650℃下3000 h热老化试验。组织和性能结果表明，所有合金的冲击吸收能量(KV₂)均随热老化进行而下降。这种塑性降低与高温下第二相演化密切相关。沿晶界先后析出M₂₃C₆和G相导致原型合金冲击韧性先下降再缓慢上升。添加W和Mo元素后，沿晶界析出Laves和σ相，引起KV₂下降更快；B元素可细化晶界σ相，使得冲击韧性下降幅度小于不含B元素。加入Al元素后，合金基体中析出大量Laves和NiAl相，同时晶界σ相快速粗化，导致材料脆化严重。     

α/γ相比率调控对超音速等离子喷涂Al2O3阻氚涂层微结构及性能的影响

采用超音速等离子喷涂技术在中国低活化马氏体钢表面制备不同α/γ相比率的Al₂O₃阻氚涂层,研究了α/γ相比率调控对Al₂O₃涂层微观结构、力学性能和耐电化学腐蚀性能的影响。利用掠入射X射线衍射（GIXRD）和扫描电子显微镜（SEM）表征Al₂O₃涂层的微观结构、粘结拉伸试验法和纳米压痕仪表征涂层的力学性能、动电位极化曲线法测试涂层的耐电化学腐蚀性能。研究结果显示：通过调控特征喷涂参数（CPSP）,Al₂O₃涂层中α相含量从78.6%至24.4%可控调节,且孔隙率从2.8%降低至1.5%;α相含量为78.6%的Al₂O₃涂层硬度为(11.500±0.575) GPa,约为高γ相含量(75.6%)涂层的2倍;且高α相含量(78.6%)涂层的腐蚀电流密度较高γ相含量(75.6%)涂层的腐蚀电流密度低1个数量级。以上结果表明,高α相含量(78.6%)的Al₂O₃涂层具有更优异的力学性能、耐电化学腐蚀性能以及耐Cl^-扩散穿透能力,具有应用于聚变堆结构材料表面阻氚涂层的潜能。     

基于卷积神经网络模型的Gd2O3/6061Al中子屏蔽材料的力学性能预测

提出了一种卷积神经网络模型来预测Gd₂O₃/6061Al中子屏蔽材料的力学性能。以Gd₂O₃/6061Al中子屏蔽材料的EBSD微观形貌及其相应的拉伸性能作为数据集来训练及验证卷积神经网络模型。结果表明：使用多个显微图像,不需任何人工图像处理,卷积神经网络可得到良好的训练结果,其性能优于传统的测试方法;卷积神经网络捕捉到晶粒的存在和晶粒的一些统计信息;晶粒数目和晶粒大小之间具有很强的相关性。     

中子俘获反应截面在线测量技术研究

利用γ全吸收型4π BaF₂探测装置,对中子俘获反应截面进行了在线测量。基于HI-13串列加速器提供的脉冲化质子束,通过⁷Li(p,n) ⁷Be反应产生中子,构建了keV能区中子源实验条件,经屏蔽准直后的中子轰击样品,应用4π BaF₂装置在线测量(n,γ)反应复合核退激时释放的瞬发γ射线级联,测量了Au、C、Nb、空白等样品。通过计算⁹³Nb(n,γ)⁹⁴Nb和¹⁹⁷Au(n,γ)¹⁹⁸Au两个反应的截面数据比值并与文献数据比对,检验了4π BaF₂探测装置和(n,γ)反应截面在线测量技术,为在中国散裂中子源（CSNS）上顺利开展(n,γ)反应截面数据测量工作提供了技术支持。     

235UF6和238UF6同位素分子共振能量转移研究

本文利用长程力碰撞理论计算了²³⁵UF₆和²³⁸UF₆同位素分子间ν₃振动能量的近共振碰撞转移过程,得到了不同温度下共振函数随能量差变化的曲线,发现共振函数的宽度随温度的升高而增大。计算了不同温度下共振转移几率和共振转移速率,发现它们随温度的升高而减小。可见,²³⁵UF₆和²³⁸UF₆同位素分子的平动会降低其共振转移几率和共振转移速率,这为激光光化学法分离铀同位素提供了理论依据。     

H2C2O4对TODGA萃取Nd3+的影响

以N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)为代表的酰胺荚醚类萃取剂可以有效萃取高放废液中的An(Ⅲ)和Ln(Ⅲ),为防止Zr⁴⁺、Pd²⁺等裂片元素萃入有机相,通常需要加入H₂C₂O₄作为水相络合剂,目前,H₂C₂O₄对TODGA萃取Ln(Ⅲ)的影响尚未报道。本工作研究了HNO₃、H₂C₂O₄浓度对TODGA或TODGA+TBP体系萃取Nd³⁺的影响,同时测定了有机相中的H₂C₂O₄浓度,并用紫外-可见吸收光谱分析了有机相中的H₂C₂O₄与有机相中Nd³⁺的配位情况。研究结果表明：HNO₃浓度在1.0~3.0 mol/L的范围内,Nd³⁺的分配比D(Nd³⁺)随HNO₃浓度的增加而增加;H₂C₂O₄浓度在0.1~0.5 mol/L的范围内,D(Nd³⁺)随H₂C₂O₄浓度的增加而增加。HNO₃浓度在1.0~3.0 mol/L的范围内,萃入有机相中H₂C₂O₄浓度随HNO₃浓度的增加而减小,且存在于有机相中的H₂C₂O₄并未与有机相Nd³⁺配位。     

Fe(OH)3胶体对铀的吸附行为

为研究地浸采铀工艺过程中Fe(OH)₃胶体对铀的吸附,利用在无水乙醇中制备的Fe(OH)₃胶体,研究了pH值、初始铀浓度及吸附时间等对Fe(OH)₃胶体吸附铀的影响。采用准一级、复合二级与Elovich动力学模型对数据进行了动力学计算与分析,结果表明Elovich 动力学方程更适合描述Fe(OH)₃胶体对铀的吸附行为。采用Freundlich与Langmuir等温吸附方程对实验数据进行了热力学分析和拟合,结果表明Freundlich模型更适合描述Fe(OH)₃胶体对铀的吸附行为。综合两种等温吸附方程,推测Fe(OH)₃胶体对铀的吸附属于不均匀表面的单层物理吸附。根据激光粒度分析与SEM分析结果推测,Fe(OH)₃胶体对铀具有较强的吸附性能,吸附主要是表面吸附。     

Effect of aging at 700 °C on precipitation and toughness of AISI 321 and AISI 347 austenitic stainless steel welds

A detailed knowledge of changes in microstructures and mechanical behaviour that occur in austenitic stainless steels with or without Nb/Ti-stabilized weld during heat treatment is of great interest, since the ductility and toughness of the material may change drastically after long aging times. Two kinds of materials, i.e. AISI 321 base and without Ti-stabilized weld steel and AISI 347 base with Nb-stabilized weld steel, were compared during aging at 700 °C up to 6000 h. Both materials present increased amount of precipitate and decreased impact energy as the aging time increases. The decreased extent of impact energy with aging is almost the same for both base materials. However, it presents differences for 347 and 321 weld samples. The latter shows a more drastic decrease of impact energy than the former due to the different amount of precipitates. 321 weld sample precipitates more numerously than 347 weld sample due to the absence of stabilized Ti/Nb on the former. Large amount of carbides is formed on 321 weld sample immediately after welding. The carbides are transformed to sigma phase, which is mainly responsible for the much more sigma phase precipitation compared with other samples, after high-temperature aging. The fractographs showed, in general, brittle fracture mode in 321 weld impact-fractured specimens after aging at 700 °C for 6000 h. However, other samples show ductile fracture mode in general. Several approaches should be employed to control sigma phase precipitation in weld material. These approaches include: decreasing content of ferrite and M₂₃C₆ carbide in weld and selecting Nb added weld wire during welding.     

Investigation of Stable Al2O3 Scale on Fe-Al Aluminized Coating for Tritium Barrier

It is well known that α-Al₂O₃ phase has stablility performance, high permeation reduction factor and good resistance performance in liquid LiPb, which is considered as the reference tritium barrier coating in future fusion reactor. In order to study the formation mechanism of stable α-Al₂O₃ scales on fusion structure material, the oxidation behavior of Fe-Al aluminized coating on China Low Activated Martensitic （CLAM） steel was investigated under the oxygen partial pressure from 1 Pa to 20 kPa at the temperature of 940-980 ℃. The Al₂O₃ scales were analyzed by thermogravimetric analysis meter, grazing angle X-ray diffractometer, glow discharge spectrometer, focused ion beam and transmission electron microscope. A single continuous Al₂O₃ scales with the maximum thickness of about 2 000 nm was formed on the diffusion Fe-Al aluminized layer. Thermogravimetric analysis results show that the higher oxidation rate constant is achieved while increasing the oxygen partial pressure, and then oxidation rate constant decreases. The phase transformation of Al₂O₃ scales on the surface of Fe-Al aluminized coating was studied during different oxidation time ranges from 3 min to 180 min. The metastable γ-Al₂O₃ and α-（Al0.948Cr0.052）₂O₃ phases is formed in the earlier oxidation process and finally transformed to stable α-Al₂O₃ phase. The features of the transient α-（Al0.948Cr0.052）₂O₃（113） and α-Al₂O₃（113） were detected by GXRD and then confirmed by focused ion beam and transmission electron microscope.     

Effect of V and Nb on precipitation behavior and mechanical properties of high Cr steel

Employment of high Cr steel as a main structural material is considered as a way to achieve economical competitiveness of fast breeder reactors. V and Nb are believed to improve the high temperature strength of high Cr steels by precipitating as carbides and/or nitrides, namely fine MX particles. However, the long term efficiency and stability of such precipitation strengthening mechanisms provided by the fine MX particles have not been clarified yet. A series of trial products controlling V and Nb contents is produced and mechanical tests are conducted to investigate the effect of these elements on the mechanical properties and the long term stability of the MX strengthening mechanism. Before and after a long term aging process, metallurgical examinations and quantitative analyses are conducted to investigate the effect of these elements on microstructure evolutions. Based on these results, the long term efficiency and stability of the strengthening mechanisms provided by the fine MX particles are discussed. Higher strength and lower ductility are obtained with the increases of V and Nb contents, although the influence of Nb content tends to be saturated at about 0.01 mass%. MX does not grow and any new precipitates cannot be observed after aging at 873 K for 6000 h. Therefore, it is expected that MX is stable after aging at 823 K for approximately 167,000 h based on Larson-Miller parameter.     

含钆中子屏蔽材料的设计及其力学性能分析

设计了一种具有良好中子屏蔽能力、高强度及高韧性的新型中子屏蔽材料,用于吸收核电站乏燃料储存格架和乏燃料运输过程中的热中子辐射。材料通过蒙特卡罗粒子传输(输运）软件MCNP进行设计,并通过放电等离子烧结设备及热轧的方式制成了板材。MCNP模拟结果及材料热中子屏蔽测试结果表明：铝基Gd₂O₃复合材料的热中子屏蔽性能与铝基碳化硼相当。Gd₂O₃颗粒球磨后呈现μm、亚μm级甚至有些颗粒达到了nm级。随球磨时间的增加,材料的力学性能逐渐增强。X射线衍射检测发现了钆-铝合金相的生成。经TEM分析表明：材料的强化机制主要是位错强化和nm级Gd₂O₃颗粒的弥散强化,拉伸强度和伸长率分别达到了240 MPa和16%,其断口主要为韧性断裂。     

Long-term properties of reduced activation ferritic/martensitic steels for fusion reactor blanket system

Thermal aging properties of reduced activation ferritic/martensitic steel F82H was researched. The aging was performed at temperature ranging from 400 °C to 650 °C up to 100,000 h. Microstructure, precipitates, tensile properties, and Charpy impact properties were carried out on aged materials. Laves phase was found at temperatures between 550 and 650 °C and M₆C type carbides were found at the temperatures between 500 and 600 °C over 10,000 h. These precipitates caused degradation in toughness, especially at temperatures ranging from 550 °C to 650 °C. Tensile properties do not have serious aging effect, except for 650 °C, which caused large softening even after 10,000 h. Increase of precipitates also causes some degradation in ductility, but it is not critical. Large increase in ductile-to-brittle transition temperature was observed in the 650 °C aging. It was caused by the large Laves phase precipitation at grain boundary. Laves precipitates at grain boundary also degrades the upper-shelf energy of the aged materials. These aging test results indicate F82H can be used up to 30,000 h at 550 °C.     

Plasma-catalytic degradation of tetracycline hydrochloride over Mn/γ-Al2O3 catalysts in a dielectric barrier discharge reactor

A coaxial dielectric barrier discharge (DBD) reactor was used for plasma-catalytic degradation of tetracycline hydrochloride over a series ofMn/γ-Al₂O₃ catalysts prepared by the incipient wetness impregnation method. The combination of plasma and theMn/γ-Al₂O₃ catalysts significantly enhanced the degradation efficiency of tetracycline hydrochloride compared to the plasma process alone, with the 10%Mn/γ-Al₂O₃ catalyst exhibiting the best tetracycline hydrochloride degradation efficiency. A maximum degradation efficiency of 99.3% can be achieved after 5 min oxidation and a discharge power of 1.3 W, with only 69.7% by a single plasma process. The highest energy yield of the plasma-catalytic process is 91.7 gkWh⁻¹. Probable reaction mechanisms of the plasma-catalytic removal of tetracycline hydrochloride were also proposed.     

Et-Ph-BCTABipy的合成及其对Pd2+的萃取性能

合成了N，N′-二乙基-N，N′-二苯基-［2，2′-联吡啶］-6，6′-二硫代酰胺(Et-Ph-BCTABipy)萃取剂，并利用¹³C NMR和¹H NMR对其进行了表征；研究了相接触时间、萃取剂浓度、水相初始酸度和Pd²⁺浓度等因素对Et-Ph-BCTABipy萃取Pd²⁺性能的影响，利用摩尔比法确定了Et-Ph-BCTABipy与Pd²⁺所形成的配合物组成；同时，在Ln(Ⅲ)与Pd²⁺共存体系中研究了Et-Ph-BCTABipy对Pd²⁺的萃取选择性。结果表明：Et-Ph-BCTABipy在HNO₃体系中对Pd²⁺具有较强的萃取性能和较高的萃取选择性；萃取过程中Et-Ph-BCTABipy与Pd²⁺以1∶2的比例结合，其萃取平衡常数K_ex=3.42×10⁶。