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Theoretical study on segregation of Cu, Mo and W impurities and stability of impurity-vacancy pairs in bcc Fe

BCC鉄中のCu, Mo, W不純物の偏析と不純物-空孔対の安定性に関する理論的研究

都留 智仁; 阿部 陽介; 鈴木 知史; 中沢 哲也; 加治 芳行; 塚田 隆

Tsuru, Tomohito; Abe, Yosuke; Suzuki, Chikashi; Nakazawa, Tetsuya; Kaji, Yoshiyuki; Tsukada, Takashi

核融合炉における構造材料の有力な候補として期待される低放射化フェライト鋼において、マトリクス中の不純物の安定性は照射脆化等の材料劣化に寄与する大きな要因である。本研究では、圧力容器等に用いられるフェライト鋼と低放射化フェライト鋼における不純物元素の析出特性と、空孔ペアとの安定性について第一原理計算を用いた検討を行った。その結果、Feマトリクス中の相互作用係数と析出エンタルピーの評価から、WやMoはCuなどの閉殻系と異なり固溶状態が安定であることがわかった。

Reduced activation ferritic steel is one of the leading structural material candidates for a nuclear fusion reactor. Since the solute impurities have an effect on the embrittlement through segregation under irradiation, the stability of impurity elements should be elaborated. In the present study the segregation characteristics of tungsten and some general solute impurities in bcc iron were investigated nonempirically by first principle calculations, where the equilibrium segregation was considered via a regular solution model and the change in enthalpy for segregation were directly evaluated for comparison. Subsequently the energetic stabilities of impurity-impurity and impurity-vacancy pair were evaluated. The segregation enthalpy is influenced by the electronic interaction between the d-electron of Fe and the outer electron of the impurity element, and molybdenum and tungsten tend to prevent from the impurity segregation.

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パーセンタイル:87.73

分野:Materials Science, Multidisciplinary

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