3D shape and orientation of nanoscale Pb inclusions at grain boundaries in Al observed by TEM and STEM tomography

Abstract

We have combined high-angle annular dark field/scanning transmission electron microscopy (HAADF-STEM) tomography with bright field (BF)-TEM tomography to characterize small inclusions of Pb at a grain boundary in Al. It was found that the shape of the grain boundary inclusions is more complex than previously thought. By using moiré fringes observed at some orientations of the specimen in a BF-TEM tomographic tilt series, we were able to determine the orientation of each grain, the axis and angle of misorientation of the grain boundary, and the facet planes of the grain boundary inclusions. The 3D shape of the inclusions was determined by merging this information with the HAADF-STEM tomography.

Keywords:

• grain boundary
• nanoscale inclusion
• TEM
• tomography
• Al–Pb alloy

Acknowledgements

We thank N.D. Browning at UC-Davis, and M.B. Braunfeld and D.A. Agard at UC-San Francisco for helpful discussions and P. Ochin of the CNRS in Vitry for providing the melt-spun alloy. T.M. was supported as a Japan Society for the Promotion of Science (JSPS) research fellow, and acknowledges the assistance of the staff and the use of the facilities at NCEM, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division of the U.S. Department of Energy under Contract No. DE-AC02-05CH1123. This study was partially supported by a Grant-in-Aid for Scientific Research in Priority Area “Nano Materials Science for Atomic Scale Modification 474” and Young Scientists (B) 20760449, from the Ministry of Education, Sports, and Culture of Japan.