Grain boundary (GB) migration plays an important role in modifying the microstructures and the related properties of polycrystalline materials, and is governed by the atomistic mechanism by which the atoms are displaced from one grain to another. Although such an atomistic mechanism has been intensively investigated, it is still experimentally unclear as to how the GB migration proceeds at the atomic scale. With the aid of high-energy electron-beam irradiation in atomic-resolution scanning transmission electron microscopy, we controllably triggered the GB migration in α-Al2O3 and directly visualized the atomistic GB migration as a stop motion movie. It was revealed that the GB migration proceeds by the cooperative shuffling of atoms on GB ledges along specific routes, passing through several different stable and metastable GB structures with low energies. We demonstrated that GB migration could be facilitated by the GB structural transformations between these low-energy structures.
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The data that support the findings of this study are available within the article and its Supplementary Information. Any other relevant data are also available upon reasonable request from the corresponding authors.
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We thank S. Kondo and E. Tochigi from the University of Tokyo for useful discussion. We also acknowledge A. Kumamoto from the University of Tokyo for his technical support with the electron microscope. This work was supported by Grants-in-Aid for Specially Promoted Research (Grant no. JP17H06094), and Grant-in-Aid for Scientific Research on Innovative Areas (Grant no. JP19H05788 and JP19H05786). B.F. acknowledges a Grant-in-Aid for Early-Career Scientists (JP18K13982) from the JSPS. This work was supported by the Nanotechnology Platform project by the Ministry of Education, Culture, Sports, Science and Technology of Japan (grant no. JPMXP09A20UT0146). A part of this work was also supported by the Elements Strategy Initiative for Structural Materials (ESISM) from the Ministry of Education, Culture, Sports, Science and Technology in Japan (MEXT).
The authors declare no competing interests.
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Supplementary Notes 1 and 2, Figs. 1–6, captions of Videos 1–3 and references.
Movie sequentially showing the step-by-step images in Supplementary Fig. 1 at 0.5 second per frame.
Movie sequentially showing the step-by-step images in Supplementary Fig. 1 in higher magnification at 0.5 second per frame.
Schematic movie for the atomistic and structural transformation process of GB migration.
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Wei, J., Feng, B., Ishikawa, R. et al. Direct imaging of atomistic grain boundary migration. Nat. Mater. (2021). https://doi.org/10.1038/s41563-020-00879-z