Vacancy Formation and Diffusion in FeCr Alloys

Abstract:

In this work we investigate the effect of chromium on the self‑diffusion of Fe and Cr in binary bcc FeCr alloys using ab initio (density‑functional) calculations. While diffusion data for FeCr systems exist, most are limited to selected compositions or rely on semi-empirical parameterisations, and a consistent ab initio assessment of vacancy-mediated Fe and Cr transport across the dilute to intermediate Cr range is still lacking. We also analyse the influence of chromium concentration on the lattice parameter of these alloys. The lattice parameter shows a clearly non‑linear dependence on Cr content: it increases steeply with chromium addition up to about 8 at.% and then remains almost constant up to the highest considered concentration of 25 at.%. The vacancy formation energy on Cr sites decreases markedly from 2.27 eV to 1.95 eV as the chromium content is raised from 7.4 at.% to 26 at.%. In contrast, the vacancy formation energy on Fe sites exhibits only a small increase between 7.4 at.% and 11 at.% Cr and then remains nearly unchanged up to 26 at.% Cr. These results indicate that chromium additions strongly facilitate the formation of vacancies on Cr sites and therefore are expected to enhance Cr self‑diffusion, whereas the self‑diffusion of Fe is only weakly sensitive to composition in the studied range. Based on the calculated activation energies, Arrhenius‑type temperature dependences were constructed for the Fe and Cr diffusion coefficients in five model alloys: Fe-7.41 at. % Cr, Fe-11.11 at. % Cr, Fe-18.52 at. % Cr and Fe-25.93 at. % Cr. The resulting diffusion coefficients are in good agreement with available experimental and theoretical data, which supports the reliability of the present ab initio-based approach for describing vacancy‑mediated transport in α‑FeCr alloys. Combining the calculated vacancy formation energies with literature data on vacancy migration energies allows us to construct Arrhenius‑type estimates for Fe and Cr self‑diffusion coefficients in α‑FeCr alloys, which are relevant for modelling microstructural evolution in ferritic steels.

• Periodical: Defect and Diffusion Forum (Volume 453)
• Pages: 89-94
• DOI: https://doi.org/10.4028/p-Js9Dbm
• Online since: July 2026
• Authors: Olga Kulitckaya*, Vladislav Kulitckii
• Keywords: Diffusion, FeCr Alloys, Lattice Parameter, Vacancy Formation Energy

References

[1] R.L. Klueh: Elevated-Temperature Ferritic and Martensitic Steels and Their Application to Future Nuclear Reactors, ORNL/TM-2004/176 (Oak Ridge National Laboratory, 2004).

DOI: 10.2172/885938

[2] R.J. Kurtz, et al.: J. Nucl. Mater. Vol. 386–388 (2009), p.411–417.

[3] M. Ado, et al., in: Proc. International Conference on Nuclear Engineering (ICONE), 2019.

[4] P. Olsson, C. Domain and J. Wallenius: Phys. Rev. B Vol. 75 (2007), p.014110.

[5] S. Choudhury, L. Barnard, J.D. Tucker and D. Morgan: J. Nucl. Mater. Vol. 411 (2011), p.1–14.

[6] P. Giannozzi et al.: J. Chem. Phys. Vol. 152 (2020), p.154105.

[7] W.B. Pearson: A Handbook of Lattice Spacings and Structures of Metals and Alloys (Pergamon Press, London 1958).

[8] X.Q. Li, J.J. Zhao and J.C. Xu: Front. Phys. Vol. 7 (2012), pp.360-365.

[9] P. Olsson, I.A. Abrikosov and J. Wallenius: Phys. Rev. B Vol. 73 (2006), p.104416.

[10] H.L. Zhang, B. Johansson and L. Vitos: Phys. Rev. B Vol. 79 (2009), p.224201.

[11] D. Nguyen-Manh, A.P. Horsfield and S.L. Dudarev: Phys. Rev. B Vol. 73 (2006), p.020101.

[12] D. Terentyev, et al.: J. Nucl. Mater. Vol. 362 (2007), pp.167-173.

[13] J. Kucera, B. Million, J. Ruzickova, V. Foldyna and A. Jakobova: Acta Metall. Vol. 22 (1974), p.135.

[14] D. Terentyev: Study of Radiation Effects in FeCr Alloys for Fusion Applications Using Computer Simulations, PhD thesis (Université Libre de Bruxelles, 2006).

[15] M. Sugihara, Y. Yamazaki, S. Takaki, K. Abiko and Y. Iijima: Mater. Trans. JIM Vol. 41 (2000), pp.87-90.

DOI: 10.2320/matertrans1989.41.87

[16] V. Kulitckii, A. Schneider, O. Lukianova, G. Wilde, C.-C. Fu and S. Divinski: Acta Mater. Vol. 251 (2023), p.118883.

DOI: 10.1016/j.actamat.2023.118883