Subphase exploration for SmFe12-based permanent magnets by Gibbs energies obtained with first-principles cluster-expansion method

Satoru Enomoto; Sonju Kou; Taichi Abe; Yoshihiro Gohda

doi:10.1016/j.jallcom.2023.169849

Article Subphase exploration for SmFe12-based permanent magnets by Gibbs energies obtained with first-principles cluster-expansion method

Satoru Enomoto ; Sonju Kou ; Taichi Abe (National Institute for Materials Science) ; Yoshihiro Gohda

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Satoru Enomoto, Sonju Kou, Taichi Abe, Yoshihiro Gohda. Subphase exploration for SmFe12-based permanent magnets by Gibbs energies obtained with first-principles cluster-expansion method. JOURNAL OF ALLOYS AND COMPOUNDS. 2023, 950 (), 169849. https://doi.org/10.1016/j.jallcom.2023.169849

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By examining Gibbs free energies for various phases, phase equilibria of the Sm-Fe-Cu ternary system are examined computationally to explore grain-boundary subphases of SmFe12-based rare-earth permanent magnets that are under development. A key quantity, the mixing enthalpy is examined from first principles. We show that the B2 Sm-Cu-Fe is a candidate for the subphase, where the solubility of Fe into Sm-Cu is better described by the cluster-expansion method finding attractive Cu-Fe interaction within the B2 sublattice. In addition, it is found that the liquid phase of Sm-Cu slightly including Fe directly equilibrates with SmFe12, which is consistent with experiments. We point out the possibility of liquid-phase sintering of the SmFe12-based magnets using this liquid phase without significant composition changes by the solidification.

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