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

结果表明，在分析电镜上配以能量色散x射线能谱仪（AEM-EDS），可用于评价微结构受控材料。1. AEM-EDS方法的推广。(1)由于标准体试样的信噪比小于标准薄膜试样，其k因子误差大于标准体试样。(2)提出了一种新的外推法。它允许分析相当于聚焦光束大小的区域或具有均匀厚度的试样。(3)提出了一种快速的x射线吸收校正方法。这涉及使用外推法辅助的计算机为基础的系统的分析电子显微镜与场发射枪。2. AEM-EDS在微结构控制材料中的应用。(1)采用AEM-EDS测定了颗粒体积分数，这是影响颗粒细分散合金强化的重要参数。差分x射线吸收法适用于两类金属间化合物Ni_3（Al,Ti）和TiAl的厚度测量，这两类金属间化合物含有细小分散的沉淀颗粒。(2)研究了ni基Ni-Al-Ta合金中γ相和γ′相的相平衡。采用原子能谱仪（AEM-EDS）测定了两相合金中γ相和γ′相的化学成分。从组成中，可以得到γ相和γ′相的联接线以及γ′相中Ta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法得到的扩散系数与电子探针微分析仪（EPMA）的结果一致。结果表明，AEM-EDS适用于较低退火温度下的扩散率测量。

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.