聚变堆候选金属材料的惰性气体离子辐照损伤的研究

综述了有关核聚变反应堆材料的辐照损伤问题的研究,主要包括国产316L奥氏体不锈钢中氦的扩散与氦泡形核生长的研究、316L及低活化FeCrMn合金的高能Ar离子辐照缺陷与空洞肿胀的研究、近期开展的低活化马氏体钢和氧化物颗粒弥散强化合金的高能Ne离子辐照损伤和效应的研究成果。This paper gives a review of our recent studies on the irradiation damage induced by energetic inert-gasions in metallic materials candidate to fusion reactors. The work includes the study of helium diffusion and helium bubble formation in 316L stainless steels, the study of void formation and swelling in the low-activation Fe-Cr-Mn alloy irradiated with high-energy Ar ions, the study of irradiation damage in some low-activation Fe-based steels and ODS alloys by high-energy Ne ions.     

碳化硅中惰性气体离子辐照引起缺陷的研究

综述了有关碳化硅材料中惰性气体离子引起辐照缺陷研究的进展。包括借助多种方法对氦离子辐照的碳化硅中氦泡集团形成的剂量阈值的实验研究,基于过冷固体假设对氦泡阈值的理论解释,不同剂量氦泡的两种形态及其机理的研究,以及重惰性气体离子（Ne,Xe）辐照下缺陷演化的特点。This paper gives a review of our recent studies on the defect production in silicon carbide induced by energetic inert-gas-ion irradiation. The work includes the study of the dose threshold for helium bubble formation by combining TEM, RBS-channeling and PAS, the theoretical analysis of the dose threshold for bubble formation based on the Frozen-Matrix assumption, two types of bubble arrangement at different dose regions and the study of damage um-ion production behavior in the case of irradiation with heavier inert-gas-ions （ Ne, Xe） as a comparison to heliirradiation.     

Irradiation effect of yttria-stabilized zirconia by high dose dual ion beam irradiation

Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.     

利用HIRFL高能重离子束的核能材料辐照损伤研究

载能重离子与高能中子在材料中能够产生相似的级联碰撞损伤,加之重离子具有大的离位损伤截面和在材料样品中低的感生放射性,载能重离子束成为模拟先进核能装置内部结构材料辐照损伤的重要手段。HIRFL能区的重离子在结构材料中的射程一般远大于晶粒尺寸,因此能够产生材料体损伤,借助小样品技术可以获得材料力学性能变化（尤其辐照脆化）的有用信息,为探讨材料辐照损伤微结构和宏观力学性能变化的关联提供了重要条件。本文简要介绍了近年来我们基于HIRFL高能离子束开展的聚变堆候选材料辐照损伤的研究,包括低活化钢的辐照脆化行为、氧化物弥散强化（ODS）铁素体钢的结构优化对于抗辐照性能的影响、不同载能粒子辐照条件下铁素体/马氏体钢的辐照肿胀数据的关联,以及高能重离子辐照的钨材料中氢同位素的滞留行为。研究表明,结合特殊的测试技术及数据分析方法,高能重离子可作为核能结构材料辐照损伤研究及评估的有效手段。Because of the similarity in cascade damage structure in materials produced by energetic heavy ions and by fast neutrons, and the high displacement rate and low induced radioactivity of samples by heavy ions, heavy ion beam becomes an important tool to simulate radiation damage by energetic neutrons in materials in advanced nuclear energy systems. The ranges of heavy ions provided by HIRFL (Heavy Ion Research Facility in Lanzhou) are generally much larger than the mean dimensions of grains in alloys candidate to advanced nuclear reactors, and is capable of producing radiation damage in bulk scale. It therefore makes possible the evaluation of change of mechanical properties including the radiation induced embrittlement from the irradiated specimens by using miniaturized specimen techniques. In the present paper, we provide an introduction of our recent studies of radiation damage of materials candidate to future fusion reactors by utilizing heavy ion beams in HIRFL.The studies include issues as follows:ductility loss of RAFM steels causes by high-energy Ne ions, impact of oxide dispersoids on the radiation resistance of ODS ferritic steels, correlation of void swelling of ferritic/martensitic steels under different particle irradiation, and behavior of deuterium retention in tungsten under irradiation with high-energy heavy ions. The results show that high-energy heavy ions can be used as a tool to efficiently investigate or evaluate radiation damage in structure materials if combined with some special test techniques and data analysis.     

高能重离子辐照的ODS铁素体钢脆化效应研究

与传统的铁素体钢相比,氧化物弥散强化(ODS) 的铁素体钢具有更优的耐高温和抗辐照性能,近年来成为先进核能装置重要的候选结构材料。在HIRFL 的扇聚焦型回旋加速器(SFC) 材料辐照终端,对一种氧化物弥散强化(ODS) 铁素体钢MA956 进行了高能Ne 离子辐照实验,旨在研究级联碰撞损伤和惰性气体原子注入条件下该材料力学性能的变化。利用辐照终端的能量衰减装置将SFC出口123.4 MeV的离子能量分解为介于38.5~121.0 MeV之间的30 个入射能量值,并通过双面辐照在厚度60 μm的样品中均匀产生了损伤。辐照剂量为9x1016 ions/cm2,在样品中的平均位移损伤为0.7 dpa,注入的Ne原子浓度为350 appm。辐照期间样品温度保持在440 ℃附近。对辐照前后的样品分别在室温和500 ℃下进行了小冲杆试验(Small-punchTest),获得了辐照前后样品的加载位移曲线,由此得到该辐照条件下样品的延性损失为18%~26%。通过扫描电子显微镜观察了断口形貌和厚度变化,估算了样品的等效断裂应变和断裂韧性。结果表明,MA956 钢经过高能Ne离子辐照后等延伸率减小,断裂韧性降低,样品发生了一定的脆化。透射电镜结果说明氧化物弥散相界面处微空洞的形成可能是导致脆化的原因。Oxide dispersion strengthened (ODS) ferritic steels have better high-temperature creep rupture strength and higher irradiation resistance than conventional ferritic steels, and show high prominence of application in advance nuclear reactors. Their stability under high-dose radiation conditions needs to be clarified. In the present study, a commercial ODS ferritic steel MA956 were irradiated with high 20Ne ions at a terminal chamber of the Sector-focused Cyclotron (SFC) at HIRFL (Heavy-ion Research Facility in Lanzhou). With the energy gradient degrader of the irradiation chamber, the primary energy (123.4 MeV) of the Ne-ion was dispersed into 30 different energies between 38.5~ 121.0 MeV, which resulted in a plateau distribution of lattice damage in the specimens. The specimens were irradiated from both sides so that the whole 60 m thickness was nearly uniformly damaged. The specimen temperature was maintained around 440 ℃ during the irradiation. The irradiation dose is about 9x1016 ions/cm2, corresponding to a damage level of 0.7 dpa and a Ne concentration of 350 appm. The specimens before and after irradiation were tested with the Small-punch Test technique, at room temperature and 500 ℃, respectively. The fracture morphology was observed by scanning electron microscopy.The results show that MA956 underwent some loss of ductility and fracture toughness after the irradiation with high-energy 20Ne ions. It may be ascribed to the formation of nano-scale cavities at the oxides/matrix interfacesin the ODS steel specimens under irradiation .     

Ne离子束辐照引起Gd2Ti2O7烧绿石体积肿胀效应研究

在液氮低温下用400 keV的Ne2+离子束对Gd₂Ti₂O₇多晶烧绿石进行了辐照实验研究, 离子束辐照量范围为5×1014—1×1016ions/cm2。利用掠X射线衍射技术对样品辐照层的结构变化进行了分析表征, X射线的掠射角分别为γ=0.25°, 0.5°, 1°和3°。结果表明: 在该实验条件的离子束辐照下, Gd₂Ti₂O₇辐照层会发生明显的体积肿胀效应, 体积肿胀程度随入射离子束辐照量的增大而增大; 在同一辐照量下, 辐照层的体积肿胀程度也随X射线入射角的增大而增大。当辐照量达到1×1016ions/cm2时, 辐照层发生非晶化相变。Polycrystalline pyrochlore Gd₂Ti₂O₇ compounds were irradiated with 400 keV Ne2+ ions at cryogenic temperature (~77 K). The irradiation fluences was ranging from 5×1014 to 1×1016 ions/cm2, corresponding to a peak ballistic damage dose of ~0.16 to 3.3 displacements per atom . Irradiation\|induced structural evolution was examined using grazing incidence X\|ray diffraction (GIXRD) at angles from 0.25° to 3° degrees. It was found that the lattice parameter increases as a function of (1) X\|ray incident angle and (2) ion irradiation fluence, suggesting that the irradiated layer is volumetrically swelled compared with the underlying un\|irradiated substrate. At ion fluence of 1×1016 ions/cm2, the irradiation layer was found to be amorphous.     

Effect of helium concentration on irradiation damage of Fe-ion irradiated SIMP steel at 300℃ and 450℃

SIMP steel is newly developed fully martensitic steel for lead-cooled fast reactors and accelerator-driven systems.It is important to evaluate its radiation resistance via high flux neutron irradiation, where dense He atoms can be formed via(n, α) transmutation reaction. Co-irradiation with Fe and He ions, instead of neutron, was performed. Specimens were irradiated with 6.4-Me V Fe ions to the damage dose of 5 dpa at a depth of 600 nm. Three different helium injection ratios of 60-appm He/dpa(dpa: displacements per atom), 200-appm He/dpa and 600-appm He/dpa at a depth of 600 nm,were performed. Two different irradiation temperatures of 300℃ and 450℃ were carried out. The effect of helium concentration on the microstructure of Fe-irradiated SIMP steel was investigated. Microstructural damage was observed using transmission electron microscopy. The formed dislocation loops and bubbles depended on the helium injection ratio and irradiation temperature. Lots of dislocation loops and helium bubbles were homogeneously distributed at 300℃, but not at 450℃. The causes of observed effects are discussed.     

Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 30OK. The nucleation and growth of helium bubble has been simulated up to 50 helium atoms. The approach to simulate the bubble growth is to add helium atoms one by one to the bubble and let the system evolve. The titanium cohesion is based on the tight binding scheme derived from the embedded atom method, and the helium-titanium interaction is characterized by fitted potential in the form of a Lennard-Jones function. The pressure in small helium bubbles is approximately calculated. The simulation results show that the pressure will decrease with the increasing bubble size, while increase with the increasing helium atoms. An analytic function about the quantitative relationship of the pressure with the bubble size and number of helium atoms is also fitted.     

快重离子辐照金红石型TiO2的肿胀效应及化学蚀刻行为研究

二氧化钛（Titatium Dioxide,简称TiO₂）晶体在中能重离子辐照时表面会出现肿胀效应, 肿胀高度与入射离子的电子能损和辐照注量有关。 辐照后的TiO₂在一定条件下能够被氢氟酸溶液化学蚀刻,化学蚀刻的电子能损阈值为8.2keV/nm,未辐照TiO₂呈现几乎零蚀刻率。要达到饱和蚀刻深度,辐照离子的注量必须大于或等于1×1013ions/cm2。采用离子辐照的潜径迹理论分析研究了辐照损伤及对化学蚀刻的影响, 快重离子辐照结合化学蚀刻是制备TiO₂微结构的有效方法。 There appears volume swelling on the surface of the irradiated rutile TiO₂ crystal and the volume swelling is affected by the ion fluence and the electronic stopping power. To induce adequate irradiation damage for the chemical etching, the irradiation parameters must fulfill some requirement. There is minimum electronic stopping power for the chemical etching of the irradiated region in TiO₂ crystal, which is about 8. 2 keV/nm. If the ion fluence is below 1×1013ions/cm2, the saturated etching depth of the irradiated region in TiO₂crystal cannot be reached. The irradiation damage based on latent track formation frame and the theoretical linkage to the etching technique is investigated. It is hopeful to fabricate micro and nano scale structurce in rutile TiO₂ crystal by using the ion irradiation and chemical etching technique.      

Defect Structures in 4H-SiC Irradiated with Highly-energetic ^20Ne^4＋ and ^120Xe^26＋ Ions

The study of damage evolution in silicon carbide bombarded with energetic helium ions is important for the use of this material in future fusion reactors. Heavier inert gas atoms like Ne and Xe have similar behavior of diffusion and clustering with helium, and the comparison of damage accumulation behavior between energetic helium and heavier inert gas ions can reveal important aspects of underlying mechanisms. As an extension of our     

Microstructure change in deuterium implanted CLAM steel induced by electron irradiation

As Reduced Activation Ferritic/Martensitic (RAFM) steel is considered the primary candidate for use as a structural material in fusion power reactors,many countries are developing different kinds of RAFM.China is developing new CLAM (China Low Activation Martensitic) steel.The study investigates microstructural changes in CLAM steel implanted with deuterium ions induced by 1250 keV electron irradiation from R.T.to 873 K,and observes both the growth and shrinkage of the defect clusters produced by deuterium ...     

Evolution,migration and clustering of helium-vacancy complexes in RAFM steel- depth resolved positron annihilation Doppler broadening study

Indian Reduced Activation Ferritic Martensitic steel is implanted with 130 keV helium ions to a fluence of 5 × 10¹⁴ and 1 × 10¹⁶ ions/cm² and investigated using positron annihilation spectroscopy. The samples were characterised by defect sensitive S and W-parameters using depth resolved slow positron beam. A dose dependency is observed in the nucleation and growth of helium bubbles with annealing temperature. An experimental evidence for the migration of smaller helium-vacancy complexes is observed via the variation in thickness/width of irradiated layer with temperature. The S–W plot clearly shows the regions corresponding to defect annealing, bubble nucleation and growth.     

Helium and point defect accumulation: (i) microstructure and mechanical behaviour

Ferritic/martensitic (F/M) steels are good candidate structural materials for the future fusion reactors and spallation sources. However, irradiation of steels is known to produce hardening, loss of ductility, shift in ductile to brittle transition temperature (DBTT) and reduction of fracture toughness and creep resistance starting at low doses. Helium (He), produced by transmutation during the irradiation, also impacts mechanical properties. Numerous experimental and theoretical studies on the evolution of the microstructure of steels under irradiation have been conducted until now. We review the effect of irradiation-induced point defects and in particular of He on the mechanical properties of F/M steels. To cite this article: R. Schäublin et al., C. R. Physique 9 (2008).     

Dissipative processes during the nonequilibrium phase transformations in martensitic thermoelastic alloys

Martensitic thermoelastic transformations are considered under nonequilibrium conditions, where a system nonmonotonically tends toward a stationary process. The specific features of a phase transformation are experimentally studied on molecular models under these nonequilibrium conditions. A resonance mode of the phase transformation, which can increase the process rate by an order of magnitude without increasing the heat source temperature, is found. The dissipative processes that occur under the monotonic and resonance conditions of martensitic thermoelastic transformations are estimated. The resonance mode is shown to be accompanied by negative entropy production and to demonstrate the self-organization of the system. These results can be used to design materials and techniques for the processing of low-potential heat sources.     

不同应力场中马氏体形核的择优取向

系统地模拟计算了不同方位四方相ZrO₂(T)椭球片分别在拉、压、剪应力诱导下发生ZrO₂(T)→ZrO₂(M)马氏体相变时系统应变能的变化.并用能量极小准则确定了有利的形核方位.结果表明相变中伴随较大的剪切变形将使马氏体形核呈现明显的择优取向;不同应力场诱导相变的临界应力相差很大. 关键词：     

Martensitic Transformations of the Titanium–Nickelide Alloys with Different Alloying Additions

Technical Physics - Martensitic transformations of the TN-10 titanium-nickelide alloys doped with V, Nb, and Ag at a level of 1 at % are studied. It is shown that the alloying elements (Ag, Nb, and...     

Microstructure evolution during surface alloying of ductile iron and austempered ductile iron by electron beam melting

Alloying and microstructural modification of surfaces by electron beam has become popular to tailor the surface properties of materials. Surface modification of as-received ductile iron, Ni-plated ductile iron and Ni-plated austempered ductile iron was carried out by electron beam melting to improve the surface properties. Martensitic structure evolved in the heat affected zone and ledeburite structure was produced in the molten zone of the ductile iron. Microhardness of the melted specimens enhanced considerably as compared to the as-received samples. However the microhardness of melted Ni-plated samples is lower than that of the unplated specimens. X-ray diffraction clearly revealed the formation of an austenite and Fe₃C phases in the electron beam molten zone. The broadening of peaks suggests refinement of the microstructure as well as internal stresses generated during electron beam melting.     

稀土离子激活长余辉发光材料的最新研究进展

长余辉发光材料是一种新型储能材料。评述了基质组成和制备技术对长余辉发光材料发光特性的影响;介绍了黄绿光、蓝光和红光长余辉材料的最新研究进展和获得长余辉发光的关键因素,即结构缺陷形成的陷阱态和稀土掺杂的作用,并对长余辉发光材料今后的研究和应用做出了展望。     

半金属磁性材料

半金属材料的一个重要特征为具有高达100%的传导电子自旋极化率。半金属磁性材料是一种具有极大的应用潜能的自旋电子学材料。本文从半金属性的来源、材料的晶体结构、半金属的电子态和电磁特性等不同角度对半金属材料进行了系统分类。对现已发现的几种半金属材料的基本性质和原子结构特征进行了综述。分别对5种传导电子自旋极化率的测量方法进行了分析和讨论。     

Solid state transformations in Fe-Ni alloys from meteorites in powder form

We report here Mössbauer studies by transmission and back-scattering technics, with Cape York and Santa Catharina meteorites in powder form. Martensitic transformation -phase to -phase is induced by mechanical treatment and long-range order is affected.