2005 Volume 46 Issue 11 Pages 2443-2448
A new observation method was developed for visualizing microstructure on a chemical mechanically polished (CMP) surface for tempered martensite of JIS-SCM440, a medium-carbon steel.
The CMP and an electropolished (EP) surfaces were observed using an atomic force microscope (AFM) and a field emission type-scanning electron microscope (FE-SEM), respectively. AFM images, FE-secondary and backscattered electron images and electron backscattered patterns (EBSP) were obtained for the CMP and EP surfaces.
The AFM and FE-secondary electron images of the EP surface clearly visualized martensite blocks and cementite particles, since unevenness corresponding to blocks and cementite particles was created by electropolishing.
On the other hand, the AFM images of the CMP surface revealed that the CMP process produced a very smooth surface with unevenness not exceeding 10 nm. The FE-backscattered electron images of the CMP surface only visualized the crystal misorientation of the martensite matrix microstructure, since the images are not influenced by surface unevenness.
The CMP surface is more appropriate than the EP surface for EBSP measurements, since the CMP surface is smoother than that of the EP surface. Blocks with a high-angle boundary exceeding 15° could be recognized by EBSP mapping, but laths with a low-angle boundary below 3° could not.