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。     

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。     

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。     

UO_2-Zr弥散燃料板氧化扩散机理研究

UO2-Zr弥散燃料板的氧化过程包括包壳与冷却剂的氧化反应和芯体中弥散的UO2燃料微球氧原子扩散过程。本文通过直接求解球坐标系下的氧化扩散方程,得到UO2燃料微球高温下向芯体中氧原子扩散强度的解析式,该式与实验数据符合良好,并结合锆水反应与UO2燃料微球高温氧原子扩散效应构建了UO2-Zr板的氧化扩散模型。新模型能预测不同的氧化结构、芯体中更高的氧原子浓度以及相对较低的氧化吸氧量,为UO2-Zr板严重事故早期行为的研究提供了理论基础。     

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。     

弥散燃料颗粒裂纹起源的有限元模拟分析

通过建立含多气泡的燃料颗粒模型,采用有限元方法分析了燃料颗粒在裂变气体气泡内压作用下的应力分布,统计了燃料颗粒内部气泡位置对气泡内壁处的最大拉应力的影响,并结合实验结果探寻了弥散燃料颗粒在辐照后退火时的裂纹起源。结果表明:当弥散燃料颗粒内部含有多个裂变气体气泡时,受气泡内压作用,气泡内壁径向应力为压应力,环向应力为拉应力;气泡位置距燃料颗粒心部越远,气泡内壁处的最大环向拉应力越大;表层气泡的最大环向拉应力远大于心部气泡的;燃料颗粒裂纹起源于表层气泡内壁。     

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。     

低活化铁素体/马氏体钢CLF-1氢氘的渗透行为

低活化铁素体/马氏体钢(RAFM钢)作为聚变堆结构材料中最有前景的候选材料,其氢同位素渗透行为备受关注。采用氢同位素气相驱动渗透的方法,对中国低活化铁素体/马氏体钢CLF-1的氢同位素渗透行为进行了研究,研究了温度、气体压强、样品表面状态等因素对其渗透行为的影响。结果表明:氢、氘在RAFM CLF-1钢中渗透扩散过程为体扩散控制,渗透率与温度的关系式均遵循Arrhenius关系;在实验测试过程中,由于样品表面发生氧化现象和缺陷捕获造成H₂和D₂渗透实验中渗透通量出现下降的现象。     

Gd1.6Nd0.4Zr2O7烧绿石的快速合成及其组织结构研究

为探索Gd₂Zr₂O₇烧绿石快速固化高放废物中锕系核素的新途径,实验用高温高压固相反应法在3～4GPa压力、1573～1673K温度范围内合成了Gd_1.6Nd_0.4Zr₂O₇烧绿石固化体,并利用X射线衍射仪、扫描电镜对样品进行了分析。结果表明：高温高压固相反应法可在极短时间（15min）内合成完全固溶的Gd_1.6Nd_0.4Zr₂O₇立方烧绿石固化体,较常用制备方法（一般合成时间不低于48h）快近200倍;用该技术合成的样品在常温常压下的相转变温度及压力得以显著提高,烧绿石相更趋稳定;样品晶格常数随Nd含量的增加及合成温度的升高而逐渐增大,随合成压力的增加而逐渐减小。这种快速高效的合成方法为未来开展高放核素的工业固化提供了一种新的技术途径和基本数据参考。     

阳离子有序相Ce2Zr2O7.97的石墨还原制备及其结构表征

采用石墨还原法探索了CeO₂-ZrO₂二元体系在不同还原温度、还原时间条件下的物相组成及结构,借助X射线衍射、红外振动光谱等手段对还原样品进行了物相表征及结构分析。实验结果表明：通过石墨还原能在较低温度（T_red＝1050 ℃）、较短时间（t＝24 h）内合成纯相Ce₂Zr₂O_7.97,较传统先还原（95%Ar+5%H₂,T_red≥1400℃,t＞48 h）后氧化（O₂或空气气氛）工艺更简单经济;Ce₂Zr₂O_7.97相能在1050～1300 ℃、24～72 h还原条件下稳定存在并保留至室温而不发生相分解,其机制可能归因于石墨所形成的弱还原环境;Ce₂Zr₂O_7.97相拥有与烧绿石Ce₂Zr₂O₇相近的有序阳离子亚晶胞结构,但由于其氧空位（O3、O4、O11）被大部分氧离子所填充,导致该相结构对称性降低。本文提出的石墨还原法制备富氧相Ce₂Zr₂O_7.97有望成为一种较传统制备工艺更简单经济的新方法,而Ce₂Zr₂O_7.97相能在还原气氛中稳定存在,可为An₂Zr₂O_7+x固化体的存放环境提供借鉴和参考。     

热处理工艺对氧化物弥散强化Fe-Cr合金微观结构和致密化的影响

将预合金粉雾化粉与Ti粉、纳米Y₂O₃粉混合后进行机械合金化,所得粉末用热等静压进行固结,采用不同的热处理参数对所得样品进行热处理。利用扫描电镜及透射电镜（TEM）等检测工具进行检测。结果表明,机械合金化中导致的孔洞会在热等静压后保留在试样基体中,随正火温度的提高,孔洞的形貌由不规则大孔洞变为细小均匀分散的小孔;在1100℃下保温5h后,孔洞粗化。TEM显示,随正火温度的提高,晶粒发生长大而粗化,并伴随着显微硬度的下降,当在1050℃后继续增加温度,则硬度变化不明显。     

12Cr-ODS钢中氧化物强化相（Y2O3）辐照损伤行为研究

本文采用电子束（e^－） 氦离子（He⁺）、氢离子（H⁺）束同时复合辐照方式研究12Cr-ODS铁素体钢中氧化物弥散强化相（Y₂O₃）辐照损伤行为,对不同辐照方式下辐照区内的氧化物形貌变化进行原位观察。研究结果表明,15dpa辐照后,氧化物周围出现微小高密度空洞,相界面变得不规则,氧化物在此特定条件下发生体积收缩或长大,尺寸有少量变化,但无明显溶解现象,对钢的性能不会产生影响。     

Preliminary Tube Manufacturing of Oxide Dispersion Strengthened Ferritic Steels with Recrystallized Structure

The effect of cold wall temperature on separative performances for ¹⁴N¹⁵N-¹⁴N₂ separation was studied with the thermal diffusion column of an effective height of 950 mm, a hot wire of 0.15 mm in radius and a cold wall of 5.0 mm in radius. The column was maintained at a constant pressure 0.1 MPa with feed flow rate of 10 cm³.min^-1 (at 0.1 MPa and 298.15 K). The temperature of the cold wall was changed from 223 to 283 K by 20 K keeping at the same temperature difference 235 K between the hot and cold walls. The total separation factor became larger as the cold wall temperature decreased, but had almost the same value at 223 K and 243 K. The experimentally obtained separation factors were compared with the results of the numerical analyses of a convection-diffusion equation. The solutions of numerical analyses with thermal diffusion factor incorporated with inelastic effect gave a good reproduction of dependence of separation factors on cut and cold wall temperature rather than those without inelastic effect. The discrepancy between experimental and analytical results, however, became larger as the cold wall temperature decreased.     

Hf对ODS-FeCrAl合金微观组织及性能的影响

为研究少量添加的Hf对ODS-FeCrAl合金微观组织及性能的影响,通过机械合金化和后续的热等静压工艺研制两种14Cr ODS FeCrAl合金,对其进行微观结构、力学性能、1 200 ℃空气抗氧化性能和1 200 ℃水蒸气抗腐蚀性能测试。TEM结果表明,两种合金中YAlO3氧化物析出相细小弥散,而Hf的添加促进合金基体中生成颗粒尺寸更加细小的Y2Hf2O7纳米氧化物。由于纳米氧化物Orowan的强化机制,两种合金均具有优异的室温与高温力学性能。XRD和SEM结果表明,两种合金经过1 200 ℃空气氧化与1 200 ℃水蒸气腐蚀后,表面均形成均匀致密的α Al2O3膜,对合金起保护作用。Hf添加有利于合金在1 200 ℃水蒸气腐蚀条件下形成更加均匀的α Al2O3膜,抑制Al3+的向外扩散,避免合金内部晶界处形成空穴。     

Effects of Grain Morphology and Texture on High Temperature Deformation in Oxide Dispersion Strengthened Ferritic Steels

Oxide Dispersion Strengthened (ODs) ferritic steel is the promising candidate alloy for long-life core materials of fast reactor. A series of experiments, such as tensile tests, creep rupture tests, texture measurements and microstructure observations, are performed for the fabricated sheets of ODs ferritic steel with simulating type of morphology and also for the cladding tube in order to clarify the origin of the peculiar strength anisotropy of the cladding tube: degraded creep rupture strength in hoop direction. From these experiments, effects of grain morphology and texture on deformation of ODs ferritic steels are evaluated.

The sheets and the cladding tube have strong texture of {001}?110? and {111}?110?, respectively. In longitudinal and transverse directions of the sheets, strength level is significantly different from each other, but crystallographic orientation is almost equivalent. From that finding, it is considered that strength anisotropy of the cladding tubes is not attributed to the texture. From the results of micro structure analysis, it is concluded that origin of the degraded creep rupture strength in transverse hoop direction of the cladding tube comes from the grain boundary sliding at the large tilt angles.     

Development of Oxide Dispersion Strengthened Steels for FBR Core Application, (II)

Previously manufactured oxide dispersion strengthened (ODS) ferritic steel cladding tubes had inferior internal creep rupture strength in the circumferential hoop direction. This unexpected feature of ODS cladding tubes was substantially ascribed to the needle-like grain structure aligned with the forming direction. In this study, the grain morphology was controlled by using the martensite transformation in ODS martensitic steels to produce an equi-axial grain structure. A major improvement in the strength anisotropy was successfully achieved. The most effective yttria addition was about 1 mass% in improving the strength of the ODS martensitic steels. A simple addition of titanium was particularly effective in increasing the strength level of the ODS martensitic steels to that of ODS ferritic steels.     

掺杂Y2O3的铁锡复合氧化物的穆斯堡尔谱学研究

采用化学共沉淀法合成α－Ｆｅ２Ｏ３－ＳｎＯ２和α－Ｆｅ２Ｏ３－ＳｎＯ２－Ｙ２Ｏ３的铁锡复合氧化物,应用Ｘ射线衍射和穆斯堡尔谱学等手段研究材料的微结构和微粒生长情况,实验结果表明,掺杂Ｙ２Ｏ３对晶粒生长有明显抑制作用,不同温度热处理可制得不同尺寸大小的纳米晶α－Ｆｅ２Ｏ３－ＳｎＯ２－Ｙ２Ｏ３材料。     

Microstructure and Mechanical Properties of Nano-Size Zirconium Carbide Dispersion Strengthened Tungsten Alloys Fabricated by Spark Plasma Sintering Method

W-(0.2,0.5,1.0)wt%ZrC alloys with a relative density above 97.5%were fabricated through the spark plasma sintering(SPS) method.The grain size of W-1.0wt%ZrC is about2.7 μm,smaller than that of pure W and W-(0.2,0.5)wt%ZrC.The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature,higher tensile strength at high temperature,and a lower ductile to brittle transition temperature(DBTT) than pure W.The tensile strength and total elongation of W-0.5wt%ZrC alloy at 700 ℃ is 535 MPa and 24.8%,which are respectively 59%and 114%higher than those of pure W(337 MPa,11.6%).The DBTT of W-(0.2,0.5,1.0)wt%ZrC materials is in the range of 500 ℃-600 ℃,which is about 100 ℃ lower than that of pure W.Based on microstructure analysis,the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening.     

硅对CLAM钢微观结构和力学性能的影响

文章研究了合金元素硅对CLAM钢的力学性能和微观结构的影响。实验表明,在CLAM钢中添加0.2％的Si会使其屈服强度和抗拉强度明显提高,同时使CLAM钢的韧脆转变温度升高,韧性降低。在光学显微镜下观察,CLAM钢呈现回火马氏体组织,Si的添加使奥氏体晶粒细化,致使CLAM钢的强度升高、韧性降低。在透射电子显微镜下观察,回火板条马氏体是其主要结构,存在针状和颗粒状两种形态的碳化物;利用透射电子显微镜选区衍射方法可知,呈颗粒状的碳化物是M23C6型碳化物。Si的添加使马氏体板条的宽度变小。     

Synthesis and Characterization of Oxide Dispersion Strengthened Ferritic Steel via a Sol-Gel Route

Nanocrystalline oxide dispersion strengthened (ODS) ferritic steel powders with nominal composition of Fe-14Cr-3W-0.3Ti-0.4Y2O3 are synthesized using sol-gel method and hy-drogen reduction.At low reduction temperature the impurity phase of CrO is detected.At higher reduction temperature the impurity phase is Cr2O3 which eventually disappears with increasing reduction time.A pure ODS ferritic steel phase is obtained after reducing the sol-gel resultant products at 1200℃ for 3h.The HRTEM and EDS mapping indicate that the Y2O3 particles with a size of about 15nm are homogenously dispersed in the alloy matrix.The bulk ODS ferritic steel samples prepared from such powders exhibit good mechanical performance with an ultimate tensile stress of 960 MPa.