High Temperature Mechanical Properties and Microstructure in 9Cr or 12Cr Oxide Dispersion Strengthened Steels

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  • Mitsuhara Masatoshi
    Department of Advanced Materials Science and Engineering, Kyushu University
  • Kurino Koichi
    Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
  • Yano Yasuhide
    Oarai Research and Development Institute, Sector of Fast Reactor and Advanced Reactor Research and Development, Japan Atomic Energy Agency
  • Ohtsuka Satoshi
    Oarai Research and Development Institute, Sector of Fast Reactor and Advanced Reactor Research and Development, Japan Atomic Energy Agency
  • Toyama Takeshi
    Institute for Materials Research, Tohoku University
  • Ohnuma Masato
    Division of Quantum Science and Engineering, Hokkaido University
  • Nakashima Hideharu
    Department of Advanced Materials Science and Engineering, Kyushu University

Bibliographic Information

Other Title
  • 9Crまたは12Cr系酸化物分散強化鋼の高温力学特性と微細組織

Description

<p>Oxide Dispersion Strengthened (ODS) ferritic steel, a candidate material for fast reactor fuel cladding, has low thermal expansion, good thermal conductivity, and excellent resistance to irradiation damage and high temperature strength. The origin of the excellent high-temperature strength lies in the dispersion of fine oxides. In this study, creep tests at 700°C or 750°C, which are close to the operating temperatures of fast reactors, and high-temperature tensile tests at 900°C to 1350°C, which simulate accident conditions, were conducted on 9Cr ODS ferritic steels, M11 and MP23, and 12Cr ODS ferritic steel, F14, to confirm the growth behavior of oxides. In the M11 and F14 creep test samples, there was little oxide growth or decrease in number density from the initial state, indicating that dispersion strengthening by oxides was effective during deformation. After creep deformation of F14, the development of dislocation substructures such as dislocation walls and subgrain boundaries was hardly observed, and mobile dislocations were homogeneously distributed in the grains. The dislocation density increased with increasing stress during the creep test. In the high-temperature ring tensile tests of MP23 and F14, the strength of both steels decreased at higher temperatures. In MP23, elongation decreased with increasing test temperature from 900°C to 1100°C, but increased at 1200°C, decreased drastically at 1250°C, and increased again at 1300°C. In F14, elongation decreased with increasing temperature. It was inferred that the formation of the δ-ferrite phase was responsible for this complex change in mechanical properties of MP23 from 1200 to 1300°C.</p>

Journal

  • Tetsu-to-Hagane

    Tetsu-to-Hagane 109 (3), 189-200, 2023

    The Iron and Steel Institute of Japan

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