Cr对离子辐照后Fe-8Cr中的位错环的影响

低活化铁素体/马氏体钢是第四代裂变堆和未来聚变堆的候选结构材料,其主要成分为Fe-8Cr合金。为了研究其辐照行为,对Fe-Cr二元合金辐照后产生的位错环进行了分析。在室温下对纯Fe和Fe-8Cr注入氦离子,随后在超高压透射电子显微镜中时效(773K/1h),并在773K进行电子束辐照并进行原位观察。结果发现,室温注氦后两种样品中产生的缺陷在773K聚集成间隙型位错环,这些位错环在随后的电子束辐照下不断长大。纯铁和Fe-8Cr中的位错环在电子束辐照下的长大速率近乎相同,但Fe-8Cr中位错环的密度比纯铁高一个数量级,而其尺寸比纯铁中的小的多。分析表明,辐照过程中Fe-8Cr中Cr团簇的富集阻止了位错环的移动。     

氘和氦离子辐照下CLAM钢的辐照硬化与微结构演变

结合先进电子显微术和纳米压痕分析,对低活化马氏体CLAM钢的辐照行为进行了研究。在室温下对CLAM钢进行了单一注D+、单一注He+以及先注D+后注He+三种方式的离子辐照。纳米压痕硬度结果显示,离子辐照后的CLAM钢均产生了明显的硬化。通过对纳米压痕硬度曲线的拟合,得到各离子辐照后的硬化率。结果表明,注D+的辐照硬化程度最低,而注He+与D+、He+共同辐照的硬化程度均很明显。微观结构分析表明,沿离子注入深度方向,辐照缺陷密度逐渐增加然后减少;在注入深度峰值附近,产生了数密度较多的缺陷。对于单独注入He+离子以及先注D+后注入He+的CLAM钢,都产生了大量细小弥散的He泡,并且由于离子协同效应后者出现深度较浅的泡;单独注入D+的CLAM钢,并没有出现泡。注He+样品中既有位错环也有He泡,硬化效应比只有位错环的注D+样品明显;而先注D+后注He+的样品,由于注D+产生的缺陷在后续注He+时会有一定的回复,硬化效果不是注D+和注He+的简单叠加,体现出协同效应。     

强流脉冲电子束作用下单晶硅表层缺陷与结构变化

为了研究超快变形诱发的非金属材料的微观结构状态,利用强流脉冲电子束(HCPEB)技术对单晶硅进行了辐照处理,并用透射电镜对电子束诱发的表层微观结构进行了分析.实验结果表明,HCPEB辐照后单晶Si表层形成了丰富的缺陷结构,互相平行的螺位错和外禀层错是辐照后最为典型的缺陷结构;同时HCPEB辐照还诱发了密度很高的包括位错圈和SFT在内空位簇缺陷,幅值极大和应变速率极高的表面应力导致的{111}面整体位移可能是大量空位簇缺陷形成的根本原因.此外,HCPEB处理可在单晶Si表面形成纳米和非晶混合结构.     

同位素效应对铁中辐照损伤的影响

有关氦与辐照缺陷的相互作用已有不少系统性的工作,但对氢与辐照缺陷的相互作用的研究不多。特别是氢的同位素氘或者氚存在于核聚变反应堆中,关于氢的同位素效应对辐照损伤的研究工作很少。采用离子加速器在室温下对纯铁注入氘离子,经500℃时效1h后,研究了电子辐照下位错环的演变过程并讨论了同位素效应对位错环偏压的影响。实验表明,随辐照剂量的增加,空位型位错环的尺寸逐渐减小直至消失。由于注氘纯铁中的位错偏压小,其空位型位错环缩小的速率比注氢纯铁中空位型位错环小,由此可以推断注氘纯铁比注氢纯铁抗辐照损伤性能好。     

奥氏体不锈钢焊接接头辐照偏析和辐照硬化的研究

为探究奥氏体不锈钢焊接接头辐照后的晶界偏析和硬化规律,实验采用剂量为2×10~(17)n/cm~2、100 keV的He~+对三组不同焊接参数的316L焊接接头进行辐照,并对其辐照前后的硬度、微观结构和晶界成分进行了表征。辐照后焊接接头的TEM结果表明出现了位错环、位错缠结、位错墙、位错胞和氦泡等辐照诱导的特征微结构,但其尺寸和密度与焊接参数并无明显的关联;晶界的EDS数据表明,辐照诱导的偏析会导致焊缝原本富Cr贫Ni的晶界出现富Ni贫Cr的现象;辐照前后的显微硬度数据表明,辐照后硬度的增量随着热输入增大而减小。因此,奥氏体不锈钢焊接接头辐照偏析和辐照后显微结构的变化与普通奥氏体不锈钢类似;晶粒尺寸随着焊接热输入减小而减小,而晶粒细化使晶粒内位错通道密度增大,辐照产生的高密度缺陷对位错滑移的阻碍作用就越明显,则辐照硬化增量会随着热输入的增大而减小。     

不同表面状态的32Cr2MoV的滑动摩擦试验比较

对复合镀膜处理的32Cr2MoV、离子氮化的32Cr2MoV和离子氮化后机械抛光的32Cr2MoV进行了滑动摩擦试验,并对比分析了三者的组织和显微硬度.结果表明,3种试样表面都呈现磨粒磨损的特征.在3种处理当中,复合镀膜的32Cr2MoV表面粗糙度比镀膜前高,但是表层0.2mm范围内镀膜后的显微硬度最高,摩擦力、摩擦系数、磨痕宽度、磨损量较离子氮化试样和离子氮化后抛光试样低,磨痕较浅,耐磨性最好.从观察结果还发现,离子氮化试样经过表面抛光后虽然表层硬度下降,但是其粗糙度远远低于抛光前,弥补了硬度下降对耐磨性的不利影响,使得其耐磨性有所提高.     

高熵合金:面向聚变堆抗辐照损伤的新型候选材料

随着核聚变技术的发展,材料的辐照损伤作为制约其发展的重要问题越来越受到人们的关注。材料在聚变堆服役时面临着高温、高密度等离子体溅射、腐蚀、中子辐照等一系列极端工况,这就要求材料具备良好的力学性能、抗中子辐照能力、抗等离子体溅射能力、耐腐蚀等诸多特性。近年来,高熵合金作为一种面向聚变堆抗辐照损伤的新型候选材料逐渐发展起来,其抗辐照损伤能力的评估以及辐照损伤机理都值得深入研究。高熵合金是一种新的合金设计理念,可通过多主元合金自身较高的熵值和原子不易扩散的特性获得热稳定性高的固溶相。高熵合金具有区别于传统合金的特性,包括高熵效应、晶格畸变效应、迟滞扩散效应以及性能上的"鸡尾酒"效应,这些特性使高熵合金具有高的强度和硬度、耐腐蚀性能、抗高温软化性能、良好的软磁性能等优势。目前高熵合金的辐照损伤研究主要通过离子辐照进行,集中在位错环演化、氦泡演化以及相稳定性的研究等方面。研究发现,离子辐照后高熵合金中的位错环、氦泡的尺寸被显著减小,这归因于高熵合金基体本身存在较大的畸变,它们作为吸附空位、氦原子等缺陷的阱缓解了辐照损伤。另外,目前针对聚变堆的高温工况,开发了以V、Hf、Ta、W等高熔点元素为主元的抗辐照难熔高熵合金体系。本文对高熵合金辐照损伤行为的研究现状与进展进行了归纳与梳理,包括高熵合金离子辐照下位错环和氦泡的演化规律、高熵合金离子辐照下基体及析出物的相稳定性、高熵合金在中子辐照下的辐照行为等,并介绍了面向聚变堆的抗辐照难熔高熵合金体系的开发与研究进展。最后对未来的研究方向进行了展望,以期为面向聚变堆的抗辐照高熵合金的开发提供参考。     

强流脉冲电子束作用下Ti2AlNb微观结构状态与耐腐蚀性能研究北大核心CSCD

利用强流脉冲电子束(HCPEB)对Ti2AlNb合金进行辐照处理,利用X射线衍射仪(XRD),场发射扫描电子显微镜(SEM),透射电子显微镜(TEM)对辐照后合金的显微组织结构进行分析,结果表明,辐照后表面形成大量火山状熔坑,随着辐照次数的增加,熔坑的密度显著减少,辐照后合金发生α+β→O相变,β和O相显著细化;辐照后表层形成了一层厚度约为4μm的重熔层,重熔层中Al发生过饱和固溶而富Al;辐照在亚表层产生高幅值的应力和温度梯度,造成亚表层发生强烈塑性变形,生成高密度的位错,孪晶和层错等缺陷结构。辐照后试样的耐腐蚀性能得到了提高,这主要归因于辐照后产生的表面净化效应和成分均匀化,表面富Al生成致密的Al_(2)O_(3)保护膜以及Al的增强扩散修复腐蚀过程中损耗的Al_(2)O_(3)膜,提高了Ti2AlNb合金的耐腐蚀性能。     

坡口形状对CLAM钢焊缝抗辐照损伤性能的影响

为探究坡口形状对中国低活化马氏体(CLAM)钢焊缝辐照损伤性能及辐照硬化性能的影响,采用扫描电子显微镜(SEM)、原子力显微镜(AFM)、透射电子显微镜(TEM)、掠入射X射线衍射(GIXRD)和纳米压痕技术等方法,研究了在室温下经能量为70 keV、剂量为1×10¹⁷ions/cm²的He⁺辐照后,V型、U型和双U型坡口CLAM钢焊缝的辐照损伤情况及力学性能。结果表明,离子辐照后,不同坡口形状焊缝金属中均产生了氦泡、析出物等缺陷,力学性能呈现出不同程度的降低。与V型和U型坡口焊缝相比,双U型坡口焊缝辐照后焊缝内部缺陷分布更均匀、尺寸更小。这是由于在三类焊缝中,双U型坡口焊缝热输入更小,焊缝晶粒组织相对较小,晶界密度更高。更高密度的晶界阻碍了缺陷间的相互聚集,减小了缺陷的尺寸。辐照后双U型坡口焊缝表面粗糙度最低,氦泡、析出物尺寸最小,衍射峰偏移量、宽化率最低,表面硬度最低,抗辐照硬化性能最好。这表明通过控制焊接坡口的形状,细化焊缝晶粒组织,可显著提升焊缝抗辐照损伤性能及抗辐照硬化性能。     

离子辐照对316L不锈钢焊缝晶体结构与力学性能的影响

目的 研究不同剂量离子辐照对不锈钢焊缝金属微观组织结构及力学性能的影响机理和影响规律.方法 通过添加3种剂量的氦离子和氘离子对316L不锈钢TIG焊焊缝金属进行辐照,分别使用XRD、纳米压痕与SEM来分析研究离子辐照对316L不锈钢焊缝金属的晶体结构、力学性能以及表面微观形貌的影响.结果 离子辐照后,焊缝金属XRD衍射...     

光谱学研究银纳米颗粒在玻璃中的生成规律

通过离子交换法将银离子引入白硅酸盐玻璃和绿硅酸盐玻璃,利用光致发光(photoluminescence-PL)和光吸收(optical absorption-OA)谱研究银离子的团簇化、成核和生长.由于白硅酸盐玻璃不含二价铁离子,因此,银纳米颗粒形成困难,颗粒体积分数非常低,以致样品中银纳米颗粒的共振吸收峰不明显.在这种条件下,样品中存在大量银离子和银的小原子团簇.在绿玻璃中,氧化铁含量较高,引入到玻璃中的银离子大部分被二价铁离子还原成中性银原子,通过热处理,银离子在玻璃中成核和生长.在相近的热处理条件下,绿玻璃有利于银纳米颗粒的生成.银纳米颗粒在形成过程中,消耗大量银离子,造成样品的发光强度逐渐降低.     

Ion irradiation hardening of C60 thin films

The nanoindentation technique is used to measure the hardness and the Young’s modulus of ion irradiated C₆₀ films, 70 nm thick, deposited on a Silicon substrate. An increase of hardness from 1.3 GPa for the pristine sample to 10 GPa after irradiation with 800 keV Bi⁺ and N²⁺ ions was observed. The Young’s modulus also increases from 60–150 GPa after the irradiation. The results are discussed in terms of the damage and amorphization produced as consequences of the electronic and nuclear energy transference due to the irradiation.     

高能电子束辐照对NBR/PVC胶圈胶料性能的影响

采用高能电子束对丁腈橡胶/聚氯乙烯(NBR/PVC)胶圈胶料进行辐照,研究不同辐照剂量对NBR/PVC胶圈胶料性能的影响。实验结果表明,生橡胶经高能电子束辐照后,焦烧时间随辐照剂量增大逐渐减小;NBR/PVC硫化胶经高能电子束辐照后,冲击弹性提高33%~67%,硬度提高4%~10%,拉伸强度提高8%左右,断裂伸长率下降6.7%~34.4%。单因素试验结果显示,50k~60kGy剂量辐照时,硫化胶拉伸强度提高幅度较大,压缩、拉伸永久变形和磨耗量下降,同时弹性、硬度均有提升。综合考虑,50k~60kGy剂量为辐照NBR/PVC胶圈硫化胶的最适剂量。     

多种重离子辐照对硼硅酸盐玻璃机械性能的影响

研究辐照导致硼硅酸盐玻璃机械性能的影响, 对高放废物的长期安全处置具有重要的意义。本工作采用0.3 MeV的P离子、4 MeV的Kr离子、5 MeV的Xe离子以及8 MeV的Au离子分别辐照硼硅酸盐玻璃, 利用纳米压痕技术表征了辐照前后样品的硬度和模量。结果表明: 硼硅酸盐玻璃的硬度和模量在一定范围内会随着辐照剂量的增大而减小, 辐照达到0.1 dpa时硬度和模量变化趋于饱和, 此时硬度下降了35%, 模量下降了18%; 而且不同种类的离子辐照对硼硅酸盐玻璃的硬度和模量造成的变化趋势基本相同。使用掠入射X射线衍射仪对样品晶态结构进行了分析, 发现辐照后硼硅酸盐玻璃仍保持非晶状态。利用Raman光谱对辐照后样品的微观结构的变化进行了表征, 发现辐照会导致玻璃网络结构发生改变, 玻璃的聚合度下降, 无序度增加。本工作还证明了离子辐照导致玻璃机械性能变化的主要因素是离子在样品中的核能量沉积导致玻璃结构的改变。     

Analysis of organometallics dispersed polymer composite irradiated with oxygen ions

Thin films of polymethyl methacrylate (PMMA) were synthesized. Ferric oxalate was dispersed in PMMA films. These films were irradiated with 80 MeV O⁶⁺ ions at a fluence of 1×10¹¹ ions/cm². The radiation induced changes in electrical conductivity, Mössbauer parameter, microhardness and surface roughness were investigated. It is observed that hardness and electrical conductivity of the film increases with the concentration of dispersed ferric oxalate and also with the fluence. It indicates that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Before irradiation, no Mössbauer absorption was observed. The irradiated sample showed Mössbauer absorption, which seems to indicate that there is significant interaction between the metalion and polymer matrix. Atomic force microscopy shows that the average roughness (R _a) of the irradiated film is lower than the unirradiated one.     

Investigation of laser irradiation effects on the hardness of Al 5086 alloy under different conditions

Laser irradiation effects on the hardness of Al 5086 alloy have been investigated by using KrF Excimer laser of 248 nm wavelength, 23 mJ pulse energy, 20 ns pulse duration, and 100 Hz repetition rate. The square-shape samples were irradiated in air as well as in vacuum (∼10⁻³ mbar) with a defocused beam of spot size 3.14 mm² at the target surface, where the laser fluence was 0.73 J/cm² and laser intensity ≈ 3.7 × 10⁷ W/cm². The number of shots were varied from 100 to 500, and its influence on the hardness profile and on the microstructure of the irradiated samples was analyzed. The surface hardness profile follows an increasing trend till 200 shots and afterwards it decreases in both the cases. The peak value of the surface hardness of laser-treated sample in air for 200 shots is 11% higher than for sample irradiated in vacuum and 48% higher than for un-irradiated sample. The surface hardness data for samples irradiated with 100-500 shots in air and in vacuum correlate very well with the dislocation line density derived from the XRD patterns, irrespective of the laser-treatment environment of samples prior to hardness measurements.     

Microstructural characterisation of alumina with Ti ion implantation

The microstructure of alumina after Ti ion implantation has been investigated. A metal vapourvacuum arc (MEVVA) ion source was employed to implant Ti ions into alumina with doses of7.6 × 10¹⁶ and 3.1 × 10¹⁷ ions/cm² at 40 kV. Scanning electronmicroscopy (SEM) of the irradiated surfaces revealed topographical changes, which were dependent ondose. The implanted layer was also characterised by Rutherford backscattering (RBS) andcross-sectional transmission electron microscopy (XTEM) which showed the lower Ti dose resulted in ahighly defective surface layer. In contrast, TiO₂ precipitates in anamorphous matrix were observed at the higher dose.     

氦离子辐照非晶态合金表面层离腐蚀研究

当Ｈｅ＾＋辐照剂量超过临界值后，非晶态合金Ｆｅ７７Ｂ１６Ｓｉ５Ｃｒ２和Ｎｉ７８Ｂ１４Ｓｉ８的表面会出现腐蚀，低剂量率辐照时，表面发泡，高剂量率辐照时，表面层离，层离后的面随剂量增加出现发泡，但泡径很小，测量了Ｈｅ在材料中的深度分布，结果表明，表面腐蚀后Ｈｅ的分布有有是单峰，有的是双峰，对双峰成因进行了讨论。     

Nanostructure formation due to impact of highly charged ions on mica

Muscovite mica was irradiated with slow highly charged Ar^q+ (charge state q = 12, 16) and Xe^q+ (q = 23, 27) ions in a kinetic energy range of 150-216 keV and subsequently observed by contact mode atomic force microscopy. Surprisingly, on samples irradiated with Xe ions nano-sized hillock-like structures were found well below the charge state threshold reported in earlier experimental investigations. However, the structures found are not the result of a true topographic surface modification induced by the ion bombardment, because the absence of these nanostructures in tapping mode images and the dependence of the detected structures on scan conditions points towards a surface modification which manifests itself only in frictional forces and therefore in height measurement artifacts. Furthermore the generated defects are not stable but can be erased by continuous scanning.     

Effect of ion irradiation on internal stress of amorphic carbon films produced by pulsed laser

Amorphic carbon films either 50 or 160 nm thick were deposited on Si(100) and glass substrates at room temperature in a high-vacuum environment using a Q-switched Nd-YAG pulse laser focused on a graphite target. These films were irradiated with Ti⁺ or C⁺ ions having kinetic energies of 35 and 75 keV, and the changes in internal stresses of the films with varying ion influence were investigated by measuring substrate bending using stylus profilometry. The ion energy and the film thickness were chosen such that the ion penetration depth, R_p, corresponded to either the film thickness or one half of the film thickness. The results indicate that there is an optimum ion fluence leading to a stress-free film for a given ion species and energy. Interpretation of the resulting stress behavior from ion irradiation was made based on the relaxation resulting from damage inside the film together with interfacial mixing. The scanning electron microscopy pictures and surface roughness measurements showed a very smooth surface for both as-deposited and ion-irradiated films. The ion-irradiated films had a Vickers hardness greater than 22 GPa, and were adherent to both Si and glass substrates. An investigation of the film characteristics using Raman scattering and electron-energy loss spectra has revealed that high-energy ion irradiation of an intermediate ion fluence can be utilized successfully to deposit an adherent and hard carbon film with controlled internal stress without changing the film structure significantly.