钨辐射损伤随辐照剂量变化的重离子辐照模拟研究

采用重离子辐照模拟方法和正电子湮没寿命测量技术研究了钨辐射损伤随辐照剂量的变化。20，60和90dpa（每个原子的位移次数）辐照损伤水平的实验结果表明，辐照在钨中产生单空位、双空位、位错和空位团等缺陷；随辐照剂量的增大，单空位、双空位和位错浓度增加，空位团的尺度和浓度都随之增大。Radiation damage in W has been studied as a function of irradiation dose by heavy ion simulation and positron annihilation lifetime measurement. The experimental results of 20, 60 and 90 dpa irradiations illustrate that the mono-and di-vacancies, dislocations and vacancy clusters are produced by the irradiation. The concentrations of the mono-and di-vacancies and dislocations and both the concentration and size of the vacancy clusters or voids all increase with the increasing of the irradiation dose.     

Fe-Cr合金辐照空洞微结构演化的相场法模拟

Fe-Cr合金作为包壳材料在高温高辐照强度等极端环境下服役,产生空位和间隙原子等辐照缺陷,辐照缺陷簇聚诱发空洞、位错环等缺陷团簇,引起辐照肿胀、晶格畸变,导致辐照硬化或软化致使材料失效.理解辐照缺陷簇聚和长大过程的组织演化,能更有效调控组织获得稳定服役性能.本文采用相场法研究Fe-Cr合金中空洞的演化,模型考虑了温度效应对点缺陷的影响以及空位和间隙的产生和复合.选择400—800 K温度区间、0—16 dpa辐照剂量范围的Fe-Cr体系为对象,研究在不同服役温度和辐照剂量下的空位扩散、复合和簇聚形成空洞的过程.在400—800 K温度区间,随着温度的升高,Fe-Cr合金空洞团簇形核率呈现出先升高后下降的趋势.考虑空位与间隙的重新组合受温度的影响可以很好地解释空洞率随温度变化时出现先升高后降低的现象.由于温度的变化将影响Fe-Cr合金中原子离位阀能,从而影响产生空位和间隙原子.同一温度下,空洞半径和空洞的体积分数随辐照剂量的增大而增大.辐照剂量的增大,级联碰撞反应加强,空位与间隙原子大量产生,高温下空位迅速的扩散聚集在Fe-Cr合金中将形成更多数量以及更大尺寸的空洞.     

质子辐照不锈钢中氢气泡产生和演化研究

采用质子辐照模拟方法和正电子湮没寿命测量方法研究了质子辐照在国产改进型316L不锈钢中产生的氢气泡及其随辐照质子注量的演化过程。5×10^12，5×10^13，5×10^14／cm^2质子辐照的实验结果表明，辐照在不锈钢中产生氢气泡的尺度随辐照质子注量增加而增大，在质子注量为5×10^14／cm^2时氢气泡尺寸达到0．62nm，气泡的浓度随质子注量增加而减小。The bubble production and evolution in the home-made modified 316L stainless steel have been investigated by the proton irradiation simulation technique and the positron annihilation lifetime measurement. The experimental results of 5 × 10^12, 5 × 10^13 and 5 × 10^14/cm^2 proton irradiations show that the produced bubble size increases, while the bubble concentration decreases, with the increasing of the irradiation proton flueence. At the proton irradiation fluence of 5 × 10^14/cm^2 the bubble size reaches 0.62 nm.     

加速器驱动嬗变研究装置中关键材料的辐照损伤分析

反应堆中各结构部件的抗辐照性能，对整个系统的使用寿命及安全性有较大的影响。本工作通过MCNPx2.70蒙特卡罗软件建立CiADS散裂靶次临界反应堆模型，结合NJOY2016核数据截面处理软件制作的材料原子离位截面，在堆芯组件数分别为30，42，72盒的情况下分别计算和分析了316L、15-15Ti、SIMP 3种不锈钢材料和ZTA陶瓷作为候选结构材料的中子辐照损伤情况。当用作CiADS燃料包壳时，3种不锈钢材料中SIMP制成的包壳的R_dpa值最小，在燃料组件数为30，42，72盒的情况下其年辐照损伤量分别约为1.16，1.61和12.0 dpa/a。而ZTA制成的燃料包壳的R_dpa值均大于不锈钢材料的辐照损伤。在散裂靶次临界反应堆耦合区域，轴向上CiADS中心管在束靶作用面附近所受到的辐照损伤最大。燃料组件数为30盒时，由316L制成的中心管的辐照损伤率峰值约为2.7 dpa/a。     

高能氩离子辐照硅产生的缺陷研究

在室温下750MeV氩离子对本征单晶硅进行辐照,通过用正电子湮没寿命测量技术、电子顺磁共振技术以及红外光吸收方法研究了辐照产生的缺陷.结果表明:电中性双空位是辐照产生的主要空位团;在4.3×10¹⁴ions/cm²的高剂量下未见样品发生非晶化转变;虽然在离子射程末端双空位的浓度随剂量的增加而显著增大,但在以电离激发过程为主要能损方式的区域里双空位的浓度基本不变.据此可以认为,电子能损过程对辐照产生的缺陷有退人作用.     

反应堆压力容器钢A508-3辐照硬化的剂量率效应研究

针对不同剂量率对国产反应堆压力容器钢(Reactor Pressure Vessel, RPV)A508-3辐照硬化的影响，利用3.5 MeV的Fe离子在3种不同剂量率(0.1, 0.5和 1.0 dpa/h)下将样品辐照至4个不同剂量点(0.1, 0.3, 1.0和3.0 dpa)，采用纳米压痕技术表征样品在不同辐照条件下的硬化效应。结果表明，在高剂量率(1.0 dpa/h)下，材料的硬度随剂量的增大快速增加，在0.3 dpa以后逐渐达到饱和；中剂量率(0.5 dpa/h)和低剂量率(0.1 dpa/h)下，样品硬度随剂量的变化趋势与高剂量率相似，但在0.3 dpa以后材料的硬度随剂量仍在缓慢增加。在辐照剂量低于0.3 dpa时，不同剂量率引起的辐照硬化差异较小，但在辐照剂量大于0.3 dpa时，不同剂量率辐照下的硬化效应差异显著。数据拟合结果表明，在实验剂量范围内辐照硬化的饱和值随剂量率的增加呈减函数关系。     

离子辐照对聚苯乙烯低温导电特性的影响

室温下用3MeV的硅离子对聚苯乙烯(PS)进行辐照,对辐照后的样品在室温至液氮温度范围的导电特性进行了测量.结果表明,当辐照剂量在1×1012cm-2附近,PS的室温电阻发生突变.随着温度的降低,PS电阻增大,在低辐照剂量下,电阻在155K附近急剧增加.对于高辐射剂量样品,在较高的温度下呈现热激活导电,在低温下电子通过隧穿传导.分析认为,PS电阻随温度的变化是由于不同剂量辐照离子在聚合物中形成的对电子传导有贡献的导电中心密度不同.通过拟合样品的渗流临界特性,分析了样品电阻随辐照剂量的变化 关键词： 聚苯乙烯 硅离子辐照 低温导电     

高能重离子辐照的低活化钢硬化效应

为了探讨聚变堆候选低活化钢的抗辐照性能,在兰州重离子加速器国家实验室HIRFL的材料辐照终端,利用63 MeV的~(14)N离子和336 MeV的~(56)Fe离子在-50?C下对一种国产低活化钢进行辐照实验.借助离子梯度减能装置,使入射离子能量在0.22—6.17 MeV/u之间变化,从而在样品表面至24μm深度范围内产生0.05—0.20 dpa的原子离位损伤坪区.利用纳米压痕仪测试样品辐照前后的显微硬度,通过连续刚度测量(constant stiffness measurement)得到低活化钢硬度的深度剖面信息.使用Nix-Gao模型很好地描述了纳米压痕硬度随深度递减的现象(压痕尺寸效应,indentation size effect),从而有效避免了低能离子辐照的软基体效应(softer substrate effect).正电子湮灭寿命谱显示低活化钢在辐照之后长寿命成分增加,说明样品中产生了大量缺陷形成空位团,从而导致了材料力学性能的变化,在离子辐照剂量增加至0.2 dpa时,平均寿命τ_m增加量逐渐变慢,材料中辐照产生的缺陷趋于饱和.     

2.5MeV的He+离子辐照316L不锈钢中氦泡的形核与生长研究

利用透射电子显微镜分析了0.3—0.5T_m温区（T_m为材料溶点）316L奥氏体不锈钢经高剂量氦离子辐照后辐照损伤峰区氦泡的形成行为.实验结果支持氦泡的双原子形核模型，并证实氦泡的形成主要受制于自间隙子/氦置换机制扩散.材料中高密度位错的存在显著增强氦泡形核并抑制氦泡生长.与前人低剂量辐照实验结果的比较表明0.3—0.5T_m温区氦泡形核机制不随辐照剂量或剂量率发生显著变化． 关键词：     

快重离子引起的辐照效应

用PAT、CEMS、SEM和TEM分析观测了HIRFL提供的能量为几十MeV到几百MeV的碳离子在Ni、马氏体时效不锈钢、HT—9铁素体钢和316L不锈钢中引起的辐照效应,包括辐照引起的偏析、脱溶、相变和肿胀,以及辐照肿胀随辐照温度的变化关系,研究了510MeV的碳离子在高纯Ni中的损伤分布,并给出了95MeV的Ar离子模拟宇宙射线在宇宙飞行器中引起数字半导体器件“软故障”的最近结果。 The radiation effects were studied by means of PAT, CEMS, SEM and TEM in nickel,martensitic ageing stainless steel, ferrite steel HT-9 and stainless steel 316L induced by carbon ionswith energy of tens of MeV to hundreds of MeV delivered by HIRFL. It includes segregate,preciptale, phase change and void swelling, as well as temperature-relativity of the irradiationswelling. The damage distribution was also studied in nickel irradiated by 510MeV C~(6+). And the recentresults of Ar ions ...     

Migration behaviour of vacancies and damage structure recovery in a Fe-based Fe-Cr-Mn-Cu-Mo multi-component alloy

ABSTRACT

A Fe-based multi-component alloy, 60Fe-12Cr-10Mn-15Cu-3Mo, which presents higher yield stress than typical stainless steels (such as 304, 316, and 340), was used to investigate the thermal stability of irradiation-induced defects. Neutron irradiation was carried out at approximately 323 and 643?K using up to 1.3 × 10^?3 and 4.5 × 10^?4 dpa (displacements per atom), respectively. While no defects were accumulated at the high temperature of 643?K, single vacancies were formed after irradiation at the low temperature of 323?K to 1.3 × 10^?3 dpa, and the vacancies became mobile at 423?K. As a result, vacancy clusters were formed. However, as the annealing temperature increased the size of vacancy clusters decreased. Coincidence Doppler broadening measurements indicated that Cu precipitates were the sites of vacancy cluster formation, and the recovery of vacancy clusters became prominent while annealing the irradiated sample at temperatures higher than 423?K. Recovery of vacancy clusters at 573?K, which was not a high temperature, was also observed even in the sample that was irradiated using 2.5?MeV Fe ions at room temperature to 0.6 dpa at damage peak.     

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.     

Effect of irradiation on microstructure and hardening of Cr–Fe–Ni–Mn high-entropy alloy and its strengthened version

ABSTRACT

A single-phase fcc high-entropy alloy (HEA) of 20%Cr–40%Fe–20%Mn–20%Ni composition and its strength with yttrium and zirconium oxides version was irradiated with 1.4?MeV Ar ions at room temperature and mid-range doses from 0.1 to 10 displacements per atom (dpa). Transmission electron microscopy (TEM), scanning transmission electron microscopy with energy dispersive X-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterise the radiation defects and microstructural changes. Nanoindentation was used to measure the ion irradiation effect on hardening. In order to understand the irradiation effects in HEAs and to demonstrate their potential advantages, a comparison was performed with hardening behaviour of 316 austenitic stainless steel irradiated under an identical condition. It was shown that hardness increases with irradiation dose for all the materials studied, but this increase is lower in high-entropy alloys than in stainless steel.     

Study of vacancy defects and their thermal stability in MeV Fe ion irradiated RAFM steel using positron beam Doppler broadening spectroscopy

Indian reduced activation ferritic-martensitic steel was irradiated with 1.1?MeV Fe ions to various doses from 1 to100?dpa at room temperature. The depth profiling of irradiation-induced vacancy-type defects and the defect-recovery under post-irradiation annealing was studied using variable low-energy positron beam Doppler broadening spectroscopy. The influence of irradiation-induced defects on the microstructural properties was studied by glancing incidence x-ray diffraction (GIXRD) and nanoindentation technique. Positron annihilation study showed the signatures of reduced vacancy concentration at the peak damage region due to injected interstitial effect from 30 to 100?dpa and the widening of vacancy-interstitial recombination-rich region towards the end of ion range with the increase in dose. The GIXRD results were analysed by modified Williamson–Hall plot method, and the variation of coherent domain size and micro-strain with irradiation dose was studied. Irradiation-induced hardening was observed in the nanoindentation study. The features observed in the GIXRD and nanoindentation study are correlated with the depth-resolved defect distribution observed in the positron annihilation study.     

Positron annihilation studies on the migration of deformation induced vacancies in stainless steel AISI 316 L

Positron lifetime measurements were carried out at room temperature before and after isochronous annealing of cylindrical, machined fatigue specimens and of round slabs of austenitic stainless steel AISI 316 L deformed in compression. Annealing experiments are evaluated in terms of vacancy migration and sinking to grain boundaries and dislocations. The model assumes spherical grains with a homogeneous initial distribution of vacancies. A vacancy migration enthalpy of H^M _V=(0.9±0.15) eV was found. It is concluded that positron trapping at dislocation lines does not significantly contribute to positron lifetime measurements at room temperature and that single vacancies are the dominating positron traps. Positron annihilation depth profiling on cross-sectional areas prepared from machined specimens using a positron microprobe with 10 μm spatial resolution shows that machining of cylindrical specimens creates vacancies up to 5 mm below the surface. Received: 11 August 2000 / Accepted: 13 November 2000 / Published online: 28 February 2001     

Investigation of radiation defects in Fe-Cr alloy

Abstract

The kinetics of radiation defect accumulation and subsequent recovery during/after electron irradiation below 273 K, at 323 K and 373 K were investigated for the Fe-15.7 at.% Cr using positron annihilation measurements at room temperature. Formation of vacancy clusters was observed at all of the irradiation temperatures. The formation of clusters and kinetics of their accumulation point to mobility of vacancies at least at room temperature. The cluster rearrangement and variations in the cluster configuration take place during annealing.     

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 Me V的离子能量分解为介于38.5～121.0 Me V之间的30个入射能量值,并通过双面辐照在厚度60μm的样品中均匀产生了损伤。辐照剂量为9×1016ions/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-punch Test),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。