Generalization of X-ray microanalysis in analytical electron microscopy and its application to microstructure-controlled materials

结果表明，分析电子显微镜配备了能量色散X射线光谱仪（AEM-EDS）是有用的微观结构控制材料的评价。1. AEM-EDS方法的推广(1)人们认识到，k因子的误差较大，使用标准的大块试样比标准的薄膜试样，因为前者的S/N比较小。(2)本文提出了一种新的外推法，它可以分析与聚焦束尺寸相当的区域或厚度均匀的试样。(3)本文介绍了一种用于场发射电子枪分析电子显微镜的X射线吸收校正的快速处理方法，即利用外推法和计算机辅助系统。2. AEM-EDS在微结构控制材料中的应用(1)用AEM-EDS测定了弥散析出相含量对合金强化的重要影响参数--弥散析出相的体积分数，用差示X射线吸收法测定了Ni_3（Al，Ti）和TiAl两种弥散析出相的厚度。(2)本文研究了Ni基Ni-Al-Ta合金中γ相和γ '相的相平衡，用AEM-EDS测定了两相合金中γ相和γ'相的化学成分，由此可以得到γ相和γ '相的结合线以及Ta在γ'相中的分配系数。(3)对Ni/Ni_3Al和Ni_3Al/ NiAl扩散偶界面进行了观察和微观分析，结果表明，AEM-EDS测量的互扩散系数与电子探针（EPMA）测量的互扩散系数基本一致，说明AEM-EDS适合于较低退火温度下的扩散系数测量。

It was shown that the analytical electron microscope equipped with an energy dispersive X-ray spectrometer(AEM-EDS)is useful for the evaluation of microstructure-controlled materials. 1. Generalization of AEM-EDS method. (1) It was recognized that the errors in k factors were larger with use of the standard bulk specimens than the standard thin-film specimens because the S/N ratio is smaller for the former. (2) A new form of the extrapolation method was presented.It permitted the analysis of a region equivalent to a focused beam size or of a specimen with a uniform thickness. (3) A rapid processing for X-ray absorption correction was presented.This involved use of the extrapolation method assisted by a computer-based system for analytical electron microscopy with a field emission gun. 2. Applications of AEM-EDS to microstructure-controlled materials. (1) The volume fraction of particles which is an important parameter for the strengthening of alloys containing fine dispersion of particles was determined by AEM-EDS.The differential X-ray absorption method was shown to be applicable to the thickness measurement of the two types of intermetallic compounds,Ni_3(Al,Ti)and TiAl,containing finely dispersed precipitate particles. (2) Phase equilibria between the gamma and gamma' phases in Ni-base Ni-Al-Ta alloys were studied.The chemical compositions of the gamma and gamma' phases in the two-phase alloys were determined by AEM-EDS.From the composition,it was possible to obtain the tie-lines for the gamma and gamma' phases and also the partitioning coefficients of Ta in the gamma' phase. (3) Observation and microanalysis were conducted across the interfaces of the diffusion couples,Ni/Ni_3Al and Ni_3Al/ NiAl.It was shown that the interdiffusivities obtained by AEM-EDS are consistent with those by an electron probe microanalyzer(EPMA).It was then demonstrated that the AEM-EDS is suitable for the diffusivity measurement at lower annealing temperatures.