Quantitative microanalysis in the analytical electron microscope and its application to the construction of alloy phase diagrams.

本文研究了用能谱仪对薄样品进行定量显微分析及其在镍基合金相图构建中的应用。为了准确和精确的量化，重要的是使用实验确定的k因子，而不是理论计算。这是因为理论方程不能描述x射线探测灵敏度的变化。样品中的x射线吸收导致定量误差很大，但这可以简单地通过外推法和x射线差分吸收法来纠正，这两种方法都不需要测量分析区域的厚度。实验表明，x射线产生的深度分布在Ni薄样品的厚度上几乎是恒定的。因此，这种影响被认为是可以忽略不计的量化镍基合金。由于在Al-X （X=Si,Cu,Ag）合金中形成了富含X元素的表面层，特别是在较薄的区域，可能会在定量中引入误差。这种表面层的影响可以通过离子铣削或使用外推法来减小。在较低温度下对Ni- al - ta三元相图的测定结果表明，γ / γ′两相区扩展到Ni浓度较高的区域。这与先前在SEM中用EPMA方法得到的结果不同。研究发现，在Ni-Al-Mo三元体系的γ / γ′两相区，当Mo总量较小时，Mo更倾向于划分为γ′相而非γ相。然而，随着Mo添加量的增加，分配行为被逆转。相中Mo的含量大于相中Mo的含量。在Ni-Al-Ta三元体系中，Ta也有类似的行为。

This study is concerned with the quantitative microanalysis of thin samples in the analyti-cal electron microscope equipped with an energy dispersive spectrometer and its application to the construction of phase diagrams in Ni-based alloys.For accurate and precise quantification, it is important to use the k-factors which are determined experimentally rather than calculated theoretically. This is because the theoretical equation cannot describe changes in the sensitivity for X-ray detection. The X-ray absorption in the sample leads to a significant error in quntification but this can be corrected simply by using the extrapolation method and the diferential X-ray absorption method, both of which do not require measurement of the thickness in analysed regions.An experiment shows that the depth distribution of X-ray production is almost constant across the thickness of Ni thin sample. Thus, this effect is considered to be negligible on the quantification Ni-base alloys.Because the formation of surface layers which are rich in X-element in Al-X (X=Si,Cu,Ag) alloys, an error may be introduced in the quantification particularly for thinner regions. The effects of such surface layer can be reduced by ion-milling or by the use of the extrapolation method.Determination of the Ni-Al-Ta ternary phase diagrams at lower temperaures results that the gamma/gamma' two phase area expands to the region of higher Ni concentration. This is different from earlier results obtained by EPMA method in SEM. It is found that, in the gamma/gamma' two phase regions of the Ni-Al-Mo ternary system, Mo is more partitioned into gamma' phase than gamma phase when the total amount of Mo is small. However, with an increasing addition of Mo, partitioning behavior is reversed. Mo is more contained in gamma phase than gamma' phase. Similar behavior is observed for Ta in the Ni-Al-Ta ternary system.