Microstructure and mechanical properties of a harmonic structure designed fe-0.3 mass%c steel

Ryohei Iritani, Kenta Hori, Bhupendra Sharma, Mie Kawabata, Guy Dirras, Tadashi Furuhara, Kei Ameyama

Research output: Contribution to journalArticlepeer-review

Abstract

The microstructure and mechanical properties of harmonic structure designed Fe-0.3mass% carbon steel was investigated. The compacts of Fe-0.3 mass% carbon steel with conventional Homogeneous structure (Homo), and Harmonic Structure (HS) consisting of fine grains (Shell) and coarse grains (Core) were fabricated by a powder metallurgy method. The mechanical milling (MM) leads to the formation of nano ferrite grains at the deformed surface of MM powder particles. After sintering, the Homo and HS compacts had ferrite (α) and perlite (P) phases. The Shell had finer α + P phases than Core, and the fraction of the P in the Shell was larger than that in the Core. It was considered that the carbon segregation occurs at the deformed surface of MM powder particles due to nano ferrite formation. As a result, the number of austenite nuclei increases in Shell. Therefore, the HS compact has both the grain size gradient as well as a phase constituent gradient. As-sintered HS indicated superior mechanical properties compared to the Homo counterparts. The mechanical properties were improved by further heat treatments. Those as-sintered and heat-treated HS compacts indicated a large increase of ductility and tensile toughness. Such outstanding and unique mechanical properties of the HS were attributed to the enhancement of the local elongation after necking. These superior mechanical properties are considered to be due to the micro and macro synergy effects.

Original languageEnglish
Pages (from-to)735-744
Number of pages10
JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
Volume106
Issue number10
DOIs
Publication statusPublished - 2020 Oct

Keywords

  • Harmonic structure
  • Heterogeneous structure
  • High strength and high ductility
  • Local elongation
  • Nano grain

ASJC Scopus subject areas

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

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