EXTENDED ABSTRACT: The microstructure of materials is one of the four major elements of concern in the discipline of materials science and engineering, and its observation and quantitative characterization is an important part of materials research, as well as a prerequisite for an in-depth understanding of the relationship between microstructure and material properties. Actual materials, especially the most widely used structural materials, are non-uniform, multifaceted and complex, with different compositions and structures at various spatial locations, leading to different properties at different scales. The essential property of material inhomogeneity requires a larger range of quantitative statistical distribution characterization of the material in order to make the conclusions formed by the organization and structure characterization more in line with the actual situation of the material. With the advancement of science and technology, there is an increasing demand for accurate characterization of the microstructure and internal complex three-dimensional spatial structure of materials. The FIB-SEM technique, which combines the high-precision cutting of focused ion beam with the high-resolution imaging of scanning electron microscope, can successfully realize the three-dimensional reconstruction of samples. However, the intrinsic property of material inhomogeneity requires a larger, multi-scale characterization of the material in order to make the characterization of the microstructure more consistent with the actual situation of the material. Based on the characteristics of uniform, rapid and layer-by-layer sputtering of glow discharge, a technique of rapid, layer-by-layer imaging preparation of large-size range of material microstructure based on glow sputtering is developed, so as to realize efficient, large-size range, layer-by-layer preparation of sample surface. The ions in the glow discharge hit the sample surface at a wide angle and in a wide range, and at the same time, compared with other ion beam methods, the average energy of the ions in the glow discharge is low, which enables uniform sputtering over a large area on the sample surface without damage to the material tissue structure; the sample can be gently, but rapidly, and controllably stripped layer by layer within a few minutes, and the microstructure of the material is revealed, so as to realize the large-area (mm-cm level) Three-dimensional reconstruction of continuous sectioning sample preparation. The conditions of glow sputtering preparation were optimized, and the effects of glow sputtering on the flatness of the sample surface and the microstructure of the material were examined from the perspectives of glow sputtering preparation, respectively. The glow discharge voltage was selected to be 1000 V, the discharge current was selected to be 100 mA, and polycrystalline high-temperature alloys were used as the research samples for the preparation of the samples. Positioning points were set on the sample surface to ensure that each glow sputtering was carried out at the same position of the sample, and the layer spacing of each sputtered layer was controlled at 3 μm by controlling the time of glow sputtering, and 20 consecutive slices of the sample were sliced for three-dimensional reconstruction by glow sputtering. A white light interferometer was used to collect the surface morphology of the samples prepared by glow sputtering in each layer to obtain the sputtering depth of the samples in that layer. The electron backscattering diffraction (EBSD) system in a double-beam scanning electron microscope (FIB-SEM) was used to acquire EBSD images of the surface of the sample prepared by glow sputtering for each layer to obtain the grain orientation of the polycrystalline high-temperature alloy material, which was used for the segmentation and identification of grains on the surface of the sample in each layer. In order to ensure the accurate acquisition of images for each layer preparation area, the localization points of the acquisition area were set by the FIB of the dual-beam EBSD microscope. An area of 200 μm × 200 μm was intercepted for 3D reconstruction of the acquired 20-layer EBSD images respectively, and the alignment of the images of different layers was carried out by the optical flow algorithm built in the 3D reconstruction software to ensure the accuracy of the 3D reconstruction, and the 3D statistical distribution characterization of the grains within the volume range of 3D reconstruction (200 μm × 200 μm × 59 μm) was successfully realized. The establishment of this method realizes the acquisition, identification and 3D reconstruction quantitative distribution characterization of the large size range of the material microstructure, which is of great scientific significance for the basic research and process improvement of materials.
Keywords：Glow sputtering; Material microstructure; Three-dimensional reconstruction characterization; New methods