Irradiation-Assisted Ostwald Ripening of Nano Oxide Particles in ODS Ferritic Steels

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K14828
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Structural/Functional materials
• Research Institution: Hokkaido University
• Principal Investigator: OONO-HORI Naoko 北海道大学, 工学研究院, 助教 (40512489)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: ODSフェライト鋼 / 酸化物粒子 / 照射 / 第一原理計算 / イオン照射 / 電子線照射

Outline of Final Research Achievements

The stability of oxide particles in ODS ferritic steels was analyzed and discussed by dividing the effects into the inherent irradiation resistance of oxides and the relative stability of oxide particles in ferritic steels, based on the idea of promoting Ostwald growth under irradiation. First-principles structural relaxation of the oxides with anti-site defects suggests that all the complex oxides, Y-Ti, Y-Al and Y-Zr, are stable. The relative stability of oxide particles in ferritic steels was evaluated by ion and electron irradiation, and the results showed that the number density of oxide particles increased under irradiation, but there are no accelerating Ostwald growth. The number density of oxide particles increased under irradiation, which may be attributed to the low solid solution limit of the oxide constituent elements in the matrix.

Free Research Field

原子力材料

Academic Significance and Societal Importance of the Research Achievements

ODSフェライト鋼は次世代高速炉・軽水炉燃料被覆管や核融合炉構造材料の有力な候補材料として、我が国のみならず世界各国で鋭意開発が進められている。フェライト鋼中に超微細分散させた酸化物粒子は熱的に安定であるが、中性子照射を受けると成長し数密度が低下するという報告がある。高温強度を担う酸化物粒子の粗大化・数密度の極端な低下は高温強度の大幅低下を招く。本研究では酸化物自身の安定性とフェライト相中の酸化物粒子の安定性に分割して解析・整理し、酸化物粒子の照射下安定性を明らかにした。