纳米尺度析出相透射电镜的统计分析技术探讨

纳米级析出相在钢中起到析出强化作用或者作为晶粒生长的抑制剂,来获得特定取向的织构,因此,对析出相进行系统分析非常重要。目前通过扫描电镜和透射电镜很难实现纳米尺度尤其是50 nm以下析出相的统计分析工作。实验通过将扫描电镜夹杂物统计的Feature软件包应用到透射电镜的能谱控制软件中,从而实现了透射电镜直接对钢中纳米尺度析出相的统计。同时对透射电镜进行析出相统计中的主要影响因素如样品制备方法、采集参数、分类方法和大面积统计方法等进行了深入研究。结果表明,实验最佳条件为采用新的复型方法制样,能谱单点采集时间为5 s,图像分辨率为2 048,连续采图统计,终止条件为析出相统计数量过100个,确定了析出相制定分类规则的具体实现方法。结合无取相电工钢W800和WH470的实验统计结果可知,其析出相种类有CuS₂和MnS+CuS₂的核壳复合析出,且实验方法能够统计分析的析出相最小尺寸为10 nm。

Discussion on statistical analysis technique of nanoscale precipitated phase by transmission electron microscope

The nanoscale precipitated phases play the role of precipitation strengthening in steel. They are also used as the inhibitor of grain growth to obtain microstructure with specific orientation. Therefore, the systemically analysis of precipitated phases is very important. At present, the statistical analysis of precipitated phases with size less than 50 nm was hardly realized by scanning electron microscope(SEM) and transmission electron microscope(TEM). In the study, the Feature software package in SEM for statistic of inclusions was applied to the energy spectrum control software of TEM, realizing the direct statistical analysis of nanoscale precipitated phases in steel by TEM. Meanwhile, the main factors influencing on the statistical analysis of precipitated phases by TEM, such as sample preparation method, acquisition parameter, classification method and large-area statistic method, were systemically studied. The results showed that the optimal experimental conditions were as follow: the new complex method was adopted for sample preparation; the single-point acquisition time of energy spectrum was 5 s; the image resolution was 2 048; the continuous map collecting statistics mode was adopted; the terminal condition was that when the statistical quantity of precipitated phases exceeded 100. The detailed implementation method for classification rules of precipitated phases was obtained. Combining the experimental statistic results of non-oriented electrical steels W800 and WH470, the type of precipitated phases was core-shell composite precipitation of CuS₂ and MnS+CuS₂. The minimum size of precipitated phases in statistical analysis by experimental method was 10 nm.