Migration energy of a self-interstitial atom in α-iron estimated by in situ observation of interstitial clusters at low temperatures using high-voltage electron microscopy

ABSTRACT

Modeling cluster dynamics or rate theory to describe the microstructural evolution of irradiated materials requires a precise knowledge of the migration energy of a self-interstitial atom (SIA), a product of energetic particle radiation. We measured the evolution of the number density of SIA clusters in electron-irradiated α-iron at low temperatures (110–320 K) by in situ observation using high-voltage electron microscopy. We identified temperature-dependent physical quantities, including (1) the peak density of SIA clusters and (2) the critical defect-free zone thickness in a thin foil specimen, associated with interstitial mobility. By fitting these quantities to the Arrhenius relations derived by rate theory analysis, we obtained estimated interstitial migration energy values of $0.26\pm 0.04$ and $0.30\pm 0.03$ eV for (1) and (2), respectively.

KEYWORDS:

• Migration energy
• self-interstitial atom
• interstitial atom cluster
• in situ observation
• high-voltage electron microscopy

Acknowledgments

We are grateful to Messrs. K. Ohkubo, T. Tanioka, R. Oota, and Y. Yamanouchi of the High Voltage Electron Microscopy Center at Hokkaido University for their technical support in the electron irradiation experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported in part by the Technology Transfer Initiative (TTI) research project (2016, 2017), Center for Advanced Research of Energy Materials, Faculty of Engineering, Hokkaido University, “Advanced Characterization Nanotechnology Platform, Nanotechnology Platform Program (MEXT)” of the High Voltage Electron Microscope Laboratory at Hokkaido University, “Interorganization Atomic Energy Research Program” of the Universities-Japan Atomic Energy Agency Joint Research Project, and JSPS KAKENHI Grant Numbers 15K06663, 17K07021, 19K05334.