Observation of three‐dimensional internal structure of steel materials by means of serial sectioning with ultrasonic elliptical vibration cutting

Abstract

SummaryA three-dimensional (3D) internal structure observation system based on serial sectioning was developed from an ultrasonic elliptical vibration cutting device and an optical microscope combined with a high-precision positioning device. For bearing steel samples, the cutting device created mirrored surfaces suitable for optical metallography, even for long-cutting distances during serial sectioning of these ferrous materials. Serial sectioning progressed automatically by means of numerical control. The system was used to observe inclusions in steel materials on a scale of several tens of micrometers. Three specimens containing inclusions were prepared from bearing steels. These inclusions could be detected as two-dimensional (2D) sectional images with resolution better than 1 μm. A three-dimensional (3D) model of each inclusion was reconstructed from the 2D serial images. The microscopic 3D models had sharp edges and complicated surfaces.

An automated three-dimensional internal structure observation system based on high-speed serial sectioning of steel materials

“…The fine shapes of inclusions in ferrous materials can be automatically and rapidly observed with our system, because the total time required to create a mirrored surface of 3 × 3 mm area and to obtain its image is only 1 min/slice. This slice speed is extraordinarily-rapid compared with previous observation using round-edge tool with 20 min/slice for the same area [14]. Moreover, when the number of cutting paths is set such that the observation area is smaller than the width of flat cutting tool's edge, the observation rate can be as fast as 30 sec/slice.…”

“…The positions of inclusions and of the inclusions' diameters have been estimated with adequate resolution, as reported in our previously serial sectioning study [14]. However, the fine shape and distribution of inclusions aligned with each other along the z-direction are difficult to resolve by means of UT alone.…”

“…For ferrous materials, we developed an observation system consisting of an ultrasonic elliptical vibration device and a microscope combined with a high-precision positioning device [14]. Figure 1 system (TOSNUC888) with NC programming.…”

“…This method creates mirrored surfaces on ferrous materials 7 even during the repeated cutting instances required for serial sectioning. We also have developed a serial sectioning system using an elliptical vibration device, which we have used to investigate inclusions in bearing steels [14].…”

3D Observation of Micro-cracks as Cleavage Fracture Initiation Site in Ferrite-pearlite Steel

“…It can promote deeper understanding in the morphology of materials than that of the conventional 2D observation. [32][33][34][35][36][37][38] However, there has not been a study to quantify the relationship between the shapes of micro-crack and microstructures in the ferrite-pearlite steels.…”