*Article* **Three-Dimensional Imaging of Metallic Grain by Stacking the Microscopic Images**

**Jinyi Lee 1,2,3, Azouaou Berkache 1,\*, Dabin Wang <sup>1</sup> and Young-Ha Hwang <sup>4</sup>**


**Abstract:** Three-dimensional observation of metal grains (MG) has a wide potential application serving the interdisciplinary community. It can be used for industrial applications and basic research to overcome the limitations of non-destructive testing methods, such as ultrasonic testing, magnetic particle testing, and eddy current testing. This study proposes a method and its implementation algorithm to observe (MG) metal grains in three dimensions in a general laboratory environment equipped with a polishing machine and a metal microscope. An image was taken by a metal microscope while polishing the mounted object to be measured. Then, the metal grains (MGs) were reconstructed into three dimensions through local positioning, binarization, boundary extraction, (MG) selection, and stacking. The goal is to reconstruct the 3D MG in a virtual form that reflects the real shape of the MG. The usefulness of the proposed method was verified using the carbon steel (SA106) specimen.

**Keywords:** 3D imaging of metal grains; non-destructive testing methods; stacking images; SA106 carbon steel
