Strength analysis of a ferrite+bainite steel by AFM ultra-micro hardness tester

Nobuo Nagashima, Kensuke Miyahara, Saburo Matsuoka, Kaneaki Tsuzaki, Toru Hara, Toshihiko Takahashi

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7 Citations (Scopus)


AFM ultra-micro hardness test, micro Vickers hardness test and TEM observation were conducted for a ferrite+bainite steel, which consists of bainite and polygonal ferrite. The results obtained are in the following. (1) AFM ultra-micro hardness tests show that nanoscopic hardness is 155 near the center of bainitic ferrite grain and increases closer to its boundary. Nanoscopic hardness is kept constant at 151 in the polygonal ferrite grain. (2) Micro-Vickers hardness tests show that macroscopic hardness is 251 and 147 for the bainite and polygonal ferrite regions, respectively. (3) TEM observations show that many carbides precipitated along the grain boundaries of bainitic ferrite and the dislocation density was almost same in both grains of bainitic and polygonal ferrite. It is suggested from the above results that the strengthening by grain boundaries is important in the bainitic ferrite and this strengthening effect is enhanced by carbides along grain boundaries.

Original languageEnglish
Pages (from-to)815-821
Number of pages7
JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
Issue number12
Publication statusPublished - 2000

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Metals and Alloys
  • Materials Chemistry


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