Roles of solute c and grain boundary in strain aging behaviour of fine-grained ultra-low carbon steel sheets

Yoshihiko Ono, Yoshimasa Funakawa, Kaneharu Okuda, Kazuhiro Seto, Naoki Ebisawa, Koji Inoue, Yasuyoshi Nagai

研究成果: Article査読

抄録

The roles of solute C and the grain boundary in the strain aging phenomenon of polycrystalline ferritic steel were investigated using Nb-bearing ULC steel sheets with a relatively low solute C content of 1-3 mass ppm and ferrite grain sizes of 9.5 μm and 183 μm at aging temperatures from 70 to 400°C. The steels exhibited two definite hardening stages. The first hardening stage appeared in both fine- and coarse-grained specimens, in which the increase in YP (?YP) became saturated at around 30 MPa. From the apparent activation energy and hardening kinetics, the hardening mechanism was assumed to be dislocation pinning by solute C atoms. The second hardening stage, significantly appeared in fine-grained specimens accompanying a large increase in the Hall-Petch coefficient; ?YP was quite large, reaching 90 MPa. Fine precipitates were not detected in aged specimens observed by TEM and 3DAP. Segregation of solute C to the grain boundaries and diffusion of Fe atoms in the grain boundaries were proposed as possible mechanisms of this second hardening. Grain-boundary hardening is assumed to be one of the hardening mechanisms in the strain aging of the polycrystalline ferritic steel.

本文言語English
ページ(範囲)42-51
ページ数10
ジャーナルTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
105
4
DOI
出版ステータスPublished - 2019 4

ASJC Scopus subject areas

  • 凝縮系物理学
  • 物理化学および理論化学
  • 金属および合金
  • 材料化学

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