单晶结构残余应力的X射线衍射分析技术

准确测定单晶材料残余应力是控制和调整单晶构件中残余应力的前提。基于弹性力学对单晶材料弹性模量与对应衍射晶面的关系进行理论分析,建立立方单晶材料的残余应力分析模型,并提出具体试验方法,以DD3单晶叶片为例,进行试验验证。结果表明：不同衍射晶面的弹性模量受独立弹性柔度系数、取向系数影响,DD3单晶叶片表面应力模型计算值与实测值间相对误差在20 MPa范围内。这种X射线衍射残余应力测定方法测定的残余应力值可靠性较高,为工程应用中测定立方单晶残余应力提供了理论依据和试验基础。     

马氏体点阵参数与含碳量的定量关系:新的X射线衍射实验研究

发现了一个多晶马氏体X射线衍射的新的实验规律 ,并能用X射线衍射理论进行满意的解释。实验现象支持低碳马氏体为体心立方结构的假说。观察到马氏体中的碳原子有序—无序分布有关的立方—正方转变 ,并且从实验上确立了该转变的临界点 ,建立了一个马氏体点阵参数随固溶碳量变化的新经验方程。本文的实验方法及根据实验数据所获得的回归方程可成为钢中α相 (过饱和 )含碳量的实用的标定办法 (特别在低碳范围 )。     

外延膜的高分辨X射线衍射分析

广泛应用于半导体、铁电和光电材料中的外延结构特征以及应变和缺陷会影响外延膜的物理/化学性能。高分辨X射线衍射是对外延结构进行无损准确表征的关键技术。本文从高分辨X射线衍射与外延结构倒易空间的关系出发,重点阐述高分辨X射线衍射与普通X射线衍射的联系与区别,以强调高分辨X射线衍射特征。以铁电外延膜与衬底结构高分辨X射线衍射为例,系统分析它们的高分辨X射线衍射斑特征,包括共格生长、非共格生长、倾斜生长下衍射斑特征,以及外延膜的尺寸、外延膜的倾斜扭转和外延膜的应变对衍射斑的影响等。结合Si_1-xGe_x(x=0.1)等外延膜结构的具体分析阐述如何通过高分辨X射线衍射谱来获取外延膜结构参数,包括外延膜晶格常数、晶格错配度以及厚度和超晶格等信息。本文还系统介绍了高分辨X射线衍射中的倒易平面图的作法,以及相关的理论和实验方法,并据此获得了PbTiO₃外延膜的应力状态、畴结构、相变等结构信息。     

基于中子衍射和同步辐射X射线衍射的TWIP钢位错密度计算方法

本文详细梳理并介绍了被广泛应用于高强钢及其它结构金属材料位错密度计算的修正Williamson-Hall法,并结合中子衍射和同步辐射X射线衍射实验结果,以一种孪生诱发塑性(TWIP)钢为例,计算其在变形后的位错密度演化。本文详细介绍如何正确使用该方法以及如何避免常见的一些错误,并介绍其背后的原理及假设。     

单晶和强织构材料宏应力的X光衍射分析方法

定向凝固的镍基合金和硅、锗单晶以及取向硅钢等强织构材料的精确定向和宏应力计算一直是材料领域十分关注的问题,本文采用了一种基于单一极图识别晶体坐标系取向的方法,直接利用宏应力测算中的极角参数来确定晶体坐标系的欧拉角;讨论了将该方法和Suyama等人提出的宏应力X光衍射回归分析方法相结合的算法,使该方法更易于工程应用。     

Application of Synchrotron X-Ray Imaging and Diffraction in Additive Manufacturing: A Review

Additive manufacturing (AM) is a rapid prototyping technology based on the idea of discrete accumulation which offers an advantage of economically fabricating a component with complex geometries in a rapid design-to-manufacture cycle. However, various internal defects, such as balling, cracks, residual stress and porosity, are inevitably occurred during AM due to the complexity of laser/electron beam-powder interaction, rapid melting and solidification process, and microstructure evolution. The existence of porosity defects can potentially deteriorate the mechanical properties of selective laser melting (SLM) components, such as material stiffness, hardness, tensile strength, and fatigue resistance performance. Synchrotron X-ray imaging and diffraction are important non-destructive means to elaborately characterize the internal defect characteristics and mechanical properties of AM parts. This paper presents a review on the application of synchrotron X-ray in identifying and verifying the quality and requirement of AM parts. Defects, microstructures and mechanical properties of printed components characterized by synchrotron X-ray imaging and diffraction are summarized in this review. Subsequently, this paper also elaborates on the online characterization of the evolution of the microstructure during AM using synchrotron X-ray imaging, and introduces the method for measuring AM stress by X-ray diffraction (XRD). Finally, the future application of synchrotron X-ray characterization in the AM is prospected.     

具有择优取向性的基材表面的薄膜厚度的X射线衍射测量修正

根据薄膜对X射线的吸收效应,利用X射线衍射方法可测量出多晶基材表面的薄膜厚度。但试验结果显示,基材的择优取向效应对薄膜厚度的测量影响显著。根据理论分析,提出了择优取向修正方法。在对X射线衍射数据进行择优取向修正后,利用最小二乘法对修正后的数据进行拟合。拟合结果显示,该方法可以有效地对基材的择优取向效应进行修正,从而获得较为准确的薄膜厚度值。     

Recent Progress of Synchrotron X-Ray Imaging and Diffraction on the Solidification and Deformation Behavior of Metallic Materials

Characterizing the microstructure and deformation mechanism associated with the performances and properties of metallic materials is of great importance in understanding the microstructure-property relationship. The past few decades have witnessed the rapid development of characterization techniques from optical microscopy to electron microscopy, although these conventional methods are generally limited to the sample surface because of the intrinsic opaque nature of metallic materials. Advanced synchrotron radiation (SR) facilities can produce X-rays with strong penetrability and high spatiotemporal resolution, and thereby enabling the non-destructive visualization of full-field structural information in three dimensions. Tremendous endeavors were devoted to the 3rd generation SR over the past three decades, in which X-ray beams have been focused down to 100 nm. In this paper, recent progresses on SR-related characterization technologies were reviewed, with particular emphases on the fundamentals of synchrotron X-ray imaging and synchrotron X-ray diffraction, as well as their applications in the in situ observations of material preparation (e.g., in situ dendrite growth during solidification) and service under extreme environment (e.g., in situ mechanics). Future innovations toward next-generation SR and newly emerging SR-based technologies such as dark-field X-ray microscopy and Bragg coherent X-ray diffraction imaging were also advocated.     

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  利用磁过滤阴极电弧镀在硬质合金上沉积厚度约2~3 μm的TiAlN薄膜,并用MEVVA源离子对TiAlN薄膜注入金属离子V+和Nb+。应用北京同步辐射装置（BSRF）的同步辐射光源,采用掠入射X射线衍射（GIXRD）的方法对TiAlN薄膜表面离子注入层的微观结构进行分析研究。结果表明：未经过离子注入的TiAlN薄膜主要组成相是没有择优取向的Ti3AlN伴有少量AlN,而较小剂量(1×1017 ions/cm2)的离子注入都可以使Ti3AlN产生（111）上的择优取向和细化晶粒,且AlN消失;当离子注入的剂量达到5×1017 ions/cm2时,注入V+的Ti3AlN择优取向变为（210）,并产生TiN相;注入Nb+ 的各个衍射峰完全消失,说明TiAlN薄膜表面离子注入层被非晶化,结合透射电镜的研究结果,观察到非晶层的厚度约为80~100 nm。     

The centennial of the first X-ray crystal structures

A short account is given of the discoveries of the first crystal structures using X-ray diffraction by William Henry Bragg and William Lawrence Bragg, a father and son team working at Leeds University and Cambridge University. Their first publications, separately and together, are highlighted. This is a contribution to the centennial celebrations of these discoveries and looking towards the International Year of Crystallography to be celebrated in 2014 led by the International Union of Crystallography.     

Phase Evolution and Thermal Expansion Behavior of a γ′ Precipitated Ni-Based Superalloy by Synchrotron X-Ray Diffraction

The phase evolution and thermal expansion behavior in superalloy during heating play an essential role in controlling the size and distribution of precipitates, as well as optimizing thermomechanical properties. Synchrotron X-ray diffraction is able to go through the interior of sample and can be carried out with in situ environment, and thus, it can obtain more statistics information in real time comparing with traditional methods, such as electron and optical microscopies. In this study, in situ heating synchrotron X-ray diffraction was carried out to study the phase evolution in a typical γ′ phase precipitation strengthened Ni-based superalloy, Waspaloy, from 29 to 1050 °C. The γ′, γ, M₂₃C₆ and MC phases, including their lattice parameters, misfits, dissolution behavior and thermal expansion coefficients, were mainly investigated. The γ′ phase and M₂₃C₆ carbides appeared obvious dissolution during heating and re-precipitated when the temperature dropped to room temperature. Combining with the microscopy results, we can indicate that the dissolution of M₂₃C₆ leads to the growth of grain and γ′ phase cannot be completely dissolved for the short holding time above the solution temperature. Besides, the coefficients of thermal expansions of all the phases are calculated and fitted as polynomials.     

Crystal structures and hydrogenation behavior of （Ca0.9Sr0.08（Al1-xZnx）3 alloys

The crystal structures and hydrogenation behavior of the （Ca0.9Sr0.1）8（Al1-xZnx）3 （x = 0, 0.1, 0.2, 0.3 and 0.4） alloys were investigated. The new phase （Ca,Sr）E（Al,Zn） was found whenx 〉 0.1. （Ca, Sr）E（Al,Zn） crystallizes in space group 14/mmm （A-139）. The lattice parameters were calculated to be a = b = 1.1616（2） nm, c = 1.6422（4） nm. Zn atoms occupy the 8h and 16n sites together with Al atoms. The （Ca0.9Sr0.1）8Al3 alloy only contains a single Ca8Al3 phase. The （Ca0.9Sr0.1）8（Al1-xZnx）3 alloys consist of Ca8Al3, CasZn3, Ca and （Ca,Sr）2（Al,Zn） phases when x is from 0.1 to 0.3. As x increasing to 0.4, the alloy consists of （Ca,Sr）E（Al,Zn）, Ca8Zn3 and Ca. The hydrogenated （Ca0.9Sr0.1）8Al3 and （Ca0.9Sr0.1）8（Al0.9Zn0.1）3 samples consist of CartE and Al. The （Ca0.9Sr0.1）8（Al1-xZnx）3 （x = 0.2, 0.3 and 0.4） samples can be hydrogenated into CaH2, Al and CaZnl3 under a hydrogen pressure of 5 MPa at 473 K.     

Centennial of X-ray diffraction: development of an unpromising experiment with a wrong explanation

In February 1912 in Munich, P. P Ewald, one of A. Sommerfeld's Ph.D. students, consulted M. Laue on matters related to crystal optics, his thesis subject. During the conversation, Laue conceived the idea that a crystal might act as a three-dimensional diffraction grating to the X-rays. Despite the idea having met with scepticism among his colleagues, Laue succeeded in getting the help of two of W. C. Roentgen's doctorands: F. Friedrich, Sommerfeld's laboratory assistant, and P. Knipping: to undertake the, by now, legendary experiments that originated a new branch of Physics. The results solved two fundamental questions of the time: namely are the X-rays electromagnetic radiation (light) of very short wavelength? And also, do the crystals have spatial periodic arrangements? The affirmative answer to both questions was immediately followed in 1913 by the instrumentation and re-interpretation of the phenomenon through the pioneering work by W. H. Bragg and his son W. L. Bragg, who paved the way to the portentous development of structural crystallography by X-ray diffraction that took place during the last hundred years.