同步辐射原位X射线散射技术在纳米与能源材料中的应用

同步辐射原位X射线散射技术可以实现对材料结构进行多尺度的、无损的、高时间空间分辨率的表征,动态地揭示材料微观结构在不同外界环境下的演变过程。X射线散射基础理论已经相对成熟。第三代同步辐射光源大幅提高了X射线散射技术的时空分辨率,进一步拓宽X射线散射技术的应用场景。当前同步辐射原位X射线散射技术的难点主要集中于实验装置设计和大数据处理。概述了X射线散射技术的主要分类和基本的实验方法,主要介绍了不同分类的同步辐射原位X射线散射技术在纳米材料(纳米颗粒生长和纳米颗粒自组装)与能源材料(以钙钛矿薄膜材料为代表)研究中的应用。最后结合当前国内外先进同步辐射光源的发展现状,展望了同步辐射原位X射线散射技术未来发展的方向和应用前景。     

编者按

正同步辐射技术是近年来兴起的一种先进的研究手段,利用高能电子统周运动产生的高能量、高亮度的X射线能够探究物质的内部结构信息。同步辐射光源的各条线站均有各自的特点及适合的应用领域。基于同步辐射的原位实验成为了理解材料的成分-工艺-结构-性能之间关系的有力武器。近年来,基于同步辐射的一些新的表征方法及应用也逐步涌现,     

同步辐射高能X射线衍射在材料研究中的应用进展

同步辐射是具有连续光谱宽波段、高通量、低发散度等优点的先进脉冲X射线光源,可用于开展其它光源无法实现的诸多前沿科学研究。第三代同步辐射光源产生的高能X射线,能大幅提高衍射的倒易空间分辨率、穿透深度及时间分辨能力,实现使役条件下工程材料与部件内部多尺度微结构单元的高效原位、精确无损表征。配备满足透射几何条件、能施加多种力物性环境的原位装置,有助于建立多场耦合下材料的跨尺度力学模型。简述了同步辐射高能X射线衍射的基本原理、第三代同步辐射光源的装置与特点,介绍了高能X射线衍射在材料形变行为、相变以及再结晶等领域的研究进展。最后基于国内外先进光源的发展现状,展望了同步辐射高能X射线衍射技术进步的主要方向。     

同步辐射技术在核材料研究中的应用

先进同步辐射光源具有高通量、高相干性、高脉冲重复率等优点,将基于其的X射线衍射、小角散射、成像、谱学等表征方法与原位环境(如温度场、应力场、气氛、溶液介质等)实验装置配合,可为系统表征与评价核能系统用材料与部件的服役行为和损伤机制提供重要技术手段.核材料在高温/应力/介质/中子辐照等复杂多场环境下的服役损伤行为长期以来...     

三维X射线衍射技术与工程材料研究

第三代同步辐射光源可以产生高能X射线,实现对使役条件下工程材料内部晶体结构的原位无损表征.三维X射线衍射(3DXRD)是一种基于同步辐射技术的新兴表征技术,其采用单色高能硬X射线对多晶材料沿不同方向采集衍射信号,得到材料内部晶粒的晶体取向、空间位置、晶内局部应力张量等信息.当结合原位实验对材料进行3DXRD分析时,可以...     

同步辐射及其在无机材料中的应用进展

同步辐射是环形加速器中做循环运动的高速电子在经过弯转磁铁时, 沿电子轨道切线方向发射的电磁辐射。作为一类平台型科技基础设施, 同步辐射光源对无机材料的研究和发展起到了重要支撑作用。同步辐射实验技术已经成为现代科学技术不可或缺的研究手段, 无机材料研究是同步辐射技术的主要应用领域之一。相对于用于材料研究的常规光源来说, 同步辐射技术研究无机材料有以下优势: 1)获取的数据质量更高; 2)空间分辨和时间分辨的能力更强; 3)原位和材料服役环境更易模拟; 4)多尺度、多方面、多种类的结构信息同步获取; 5)探测新的结构特性更有可能。同步辐射实验技术有助于解决无机材料领域中的一些关键科学问题, 从而极大地推动了无机材料的研究进展。本文首先简要介绍了同步辐射光源的现状, 以及国内现有三个同步辐射装置: 北京同步辐射装置(Beijing Synchrotron Radiation Facility, BSRF)、上海同步辐射装置(Shanghai Synchrotron Radiation Facility, SSRF)和国家同步辐射实验室(National Synchrotron Radiation Laboratory, NSRL)。然后, 从X射线衍射、散射、谱学、成像等四个方面, 列举了同步辐射技术在无机材料研究中的应用实例。最后, 对同步辐射光源和结构表征技术及其在无机材料中的应用进行了总结与展望。     

同步辐射装置——上海光源及其应用

扼要介绍了第三代同步辐射装置——上海光源的主要特性、构造、第一期工程完成的七条X射线光束线站的主要性能指标、功能及应用。     

威力强大的上海光源

该文扼要介绍威力强大的第三代同步辐射装置——上海光源的主要特性、构造、第一期工程完成的7条X射线光束线站的主要性能指标、功能及适用领域等。     

同步辐射成像技术在金属材料研究中的应用

金属材料作为一类重要的结构和功能材料,在人类社会发展中一直发挥着重要的作用。研究者也一直通过多种表征技术来研究金属材料的微观组织与性能。然而,金属材料的不透明特性在很大程度上限制了研究者们对其进行实时动态表征。随着第三代同步辐射光源的发展,同步辐射成像技术以其强穿透性、高时空分辨率、无损、可视化等优势在金属材料研究领域具有显著的优越性。回顾了金属材料实时原位研究工作的发展历程,简要介绍了近十多年来同步辐射二维/三维成像技术在金属凝固行为(晶粒生长、溶质扩散等)与物理场(电场、磁场和超声场)调控、材料内部微观组织结构(枝晶、金属间化合物形貌演变,析出相空间分布等)、细观损伤行为(裂纹的萌生、扩展及断裂机制)等研究中的典型应用,展望了同步辐射光源及成像技术的发展趋势及此技术在金属材料领域应用的未来前景。     

同步辐射与分析测试

本文介绍一种大科学装置——同步辐射装置。这是一种数百人可同时在其上进行不同的科学技术实验的设备，其可达到的水平比实验室的极限水平高许多，从某些角度代表了国家的科学和技术水平。本文扼要介绍了同步辐射的特性，同步辐射装置的构造及一些主要的分析测试技术，如：X射线吸收精细结构光谱，X射线散射，高分辨X射线衍射，能量色散与时间分辨技术，聚集与微分析，成像与显微放大，综合测试原位测试及作铯对标定等。     

Void formation in metal matrix composites by solidification and shrinkage of an AlSi7 matrix between densely packed particles

Particle reinforced metals are developed as heat sink materials for advanced thermal management applications. Metal matrix composites combine the high thermal conductivity of a metal with a low coefficient of thermal expansion of ceramic reinforcements. SiC and carbon diamond particle reinforced aluminum offer suitable thermal properties for heat sink applications. These composites are produced by liquid metal infiltration of a densely packed particle preform. Wettability, interface bonding strength and thermal mismatch are critical for void formation which leads to thermal fatigue damage under operation. The evolution of voids in AlSiC and AlCD has been studied by in-situ high resolution synchrotron tomography during matrix solidification. Large irregularly shaped matrix voids form during eutectic solidification. These voids help alleviate thermal expansion mismatch stresses by visco-plastic matrix deformation during cooling to RT after solidification, if sufficient interface bonding strength is assumed.     

A new path‐dependent multiaxial fatigue model for metals under different paths

Based on the critical plane approach, a new path‐dependent multiaxial fatigue model in low‐cycle fatigue is proposed. The proposed model includes damage contribution from four sources: the normal strain amplitude, the shear strain amplitude on the critical plane, the hydrostatic mean strain and a new path‐dependent factor. The effect of mean strain is considered by the hydrostatic mean strain. The experimental data of 11 kinds of materials are used to demonstrate the effectiveness of this new model under both zero and non‐zero mean strain multiaxial loading path.     

High‐temperature low cycle fatigue damage assessment in near alpha IMI‐834 titanium alloy

In the present work, evolution of damage under high‐temperature (823 K) low cycle fatigue loading condition in near α IMI‐834 titanium alloy has been studied. The in situ damage has been experimentally measured during cyclic deformation using the alternating current potential drop (ACPD) technique. The measured damage curve has been compared with the damage curves calculated through mechanical variables such as cyclic modulus and stress amplitude. The ACPD damage curve has been found most sensitive towards high‐temperature low cycle fatigue damage evolution.     

Damage behaviour of laminated composites during fatigue loading

This study deals with the modelling of damage evolution in the carbon/epoxy laminated composites under static and fatigue loading. A cumulative damage model is developed on the basis of damage evolution due to static and fatigue during cyclic loading. A continuum damage mechanics (CDM)‐based damage model coupling with the micromechanics has been utilized to predict the fatigue behaviour of laminate composites. A multicriterion approach has been introduced to predict the damage behaviour in the longitudinal, transverse, and shear direction at the ply scale. Extensive experimental results on T300/EPL1012 carbon/epoxy laminates are prepared to characterize under static and fatigue loading and to evaluate the proposed model in different conditions. The obtained results show that at the beginning of the cyclic loading, the damage grows suddenly and increases until final failure, which justifies the proposed method is able to predict the evolution of the damage due to static and fatigue loading separately during cyclic loading. The obtained results show that considering damage due to static loading leads to more accurate results, particularly in low‐cycle fatigue.     

Fatigue behaviors of laser hybrid welded AA7020 due to defects via synchrotron X‐ray microtomography

Defect or shrinkage is known to have a detrimental effect on the fatigue resistance of casting lightweight alloys and additively manufactured or 3D printed materials. However, very few works focus on the damage mechanism of fusion welded Al alloys due to gas pores or metallurgical defects. This paper performs an investigation on the effect of porosity on the damage evolution of laser hybrid welded 7020‐T651 alloys. The critical pore size comparable with average weld grain was assumed in terms of the population and dimension of micropores. To characterize the coupling effect between gas pores and cracks, an in situ fatigue testing rig was developed to well work at the synchrotron radiation tomography system. Combining synchrotron X‐ray microtomography and fatigue resistance testing, the pore size and location were correlated with the crack initiation and crack growth path but relatively less on the long crack propagation rate. Furthermore, the interaction between the porosity and stress concentration was elucidated by using finite element simulations, which shows that the gas pore appears to be a preferred cracking site especially near the surface.     

Simulation of elevated temperature fatigue damage evolution using the finite element method for near alpha titanium alloy

The numerical estimation of evolving damage under low cycle fatigue loading condition has been performed in the near‐α titanium alloy IMI‐834 at 823 K temperature. By using the experimentally determined parameters as input, numerical simulation of fatigue damage has been performed on round specimens using finite element analysis. Coupled deformation‐damage model has been established for this alloy for simulation of damage evolution in a three‐dimensional cylindrical low cycle fatigue test specimen. The fatigue damage estimates from numerical simulation are observed to be in close agreement with the experimental results.     

Low‐cycle fatigue life prediction of various metallic materials under multiaxial loading

This paper proposed a simple life prediction model for assessing fatigue lives of metallic materials subjected to multiaxial low‐cycle fatigue (LCF) loading. This proposed model consists of the maximum shear strain range, the normal strain range and the maximum normal stress on the maximum shear strain range plane. Additional cyclic hardening developed during non‐proportional loading is included in the normal stress and strain terms. A computer‐based procedure for multiaxial fatigue life prediction incorporating critical plane damage parameters is presented as well. The accuracy and reliability of the proposed model are systematically checked by using about 300 test data through testing nine kinds of material under both zero and non‐zero mean stress multiaxial loading paths.     

考虑应变路径的多轴低周疲劳寿命预测模型

通过分析材料在多轴非比例加载下产生附加强化的机理,该文以拉扭薄壁管试件为研究对象,分析了临界平面上的应变状态,并在此基础上以塑性应变能为控制参数定义表征多轴低周疲劳寿命对应变路径依赖性的非比例度。基于多轴疲劳临界损伤面原理,应用von-Mises 准则和本文定义的应变路径非比例度参数建立起能反映应变路径对非比例附加强化影响的多轴低周疲劳寿命预测模型。利用该模型预测08X18H10T 不锈钢、Ti-6Al-4V合金、S460N 钢和2.25Cr-1Mo 钢这4 种材料的多轴疲劳寿命,并与试验值进行比较。结果表明:该模型的预测结果与试验结果吻合良好,能同时适用于比例与非比例加载,预测精度较高,便于工程应用。