Scanning electron microscopy (SEM) techniques are widely used in microstructural investigations of materials since it can provide surface morphology, topography, and chemical information. However, it is important to use correct imaging and sample preparation techniques to reveal the microstructures of materials composed of components with different polishing characteristics such as grey cast iron, graphene platelets (GPLs)-added SiAlON composite, SiC and B4 C ceramics containing graphite or graphene-like layered particles. In this study, all microstructural details of gray cast iron were successfully revealed by using argon ion beam milling as an alternative to the standard sample preparation method for cast irons, that is, mechanical polishing followed by chemical etching. The in-lens secondary electron (I-L-SE) image was clearly displayed on the surface details of the graphites that could not be revealed by backscattered electron (BSE) and Everhart-Thornley secondary electron (E-T SE) images. Mechanical polishing leads to pull-out of GPLs from SiAlON surface, whereas argon ion beam milling preserved the GPLs and resulted in smooth surface. Grain and grain boundaries of polycrystalline SiC and B4 C were easily revealed by using I-L SE image in the SEM after only mechanical polishing without any etching process. While the BSE and E-T SE images did not clearly show the residual graphites in the microstructure, their distribution in the B4 C matrix was fully revealed in the I-L SE image.
Keywords: I-L SE detector; argon ion beam milling; grey cast iron; scanning electron microscopy (SEM); silicon carbide.
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