Microstructural observation of tempered martensite in a medium-carbon low-alloy steel by atomic force microscopy

Masao Hayakawa, Toru Hara, Saburo Matsuoka, Kaneaki Tsuzaki

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Abstract

Microstructures of JIS-SCM440 steel tempered at 723 K were observed by atomic force microscopy (AFM). Two kinds of specimen surface were prepared by electrically polishing and by chemically etching. The quality of AFM images was much better on the electropolished surface because the high vertical resolution of AFM could be fully utilized. Since the electropolishing rate depends on the crystal phase and the surface orientation, prior austenite grains, packets, blocks and small precipitates were clearly distinguished on the electropolished surface, and the average block width was determined to be 0.6 μm. The density of the heterogeneously precipitated carbides along prior austenite grain boundaries was not uniform, suggesting that the nucleation of the carbides depends on the grain boundary characteristics. The apparent size of the carbides observed by AFM was larger than the actual size observed by TEM due to the effect of the tip curvature.

Original languageEnglish
Pages (from-to)460-466
Number of pages7
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Volume64
Issue number6
DOIs
Publication statusPublished - Jan 1 2000
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

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