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High-Resolution STEM Observations of Nanometer-Sized Cavities in Rapidly Solidified 304 Stainless Steel

Published online by Cambridge University Press:  21 February 2011

Thomas F. Kelly ,
Keesam Shin ,
Jung Chan Bae ,
Richard K. Noll  and
John E. Flinn
Thomas F. Kelly
Affiliation:
Department of Materials Science and Engineering Materials Science Program, University of Wisconsin, Madison, WI 53706
Keesam Shin
Affiliation:
Department of Materials Science and Engineering
Jung Chan Bae
Affiliation:
Department of Materials Science and Engineering
Richard K. Noll
Affiliation:
Materials Science Program, University of Wisconsin, Madison, WI 53706
John E. Flinn
Affiliation:
Idaho National Engineering Laboratory, EG&G Idaho, Idaho Falls, ID 83415
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Abstract

Based upon coarsening studies of larger cavities (8 nm) in a rapidly solidified 304SS, it was determined that there should be a large number of very small cavities (1–2 nm) in these materials that are too small to observe with out-of-focus imaging techniques on a conventional TEM. Out-of-focus imaging on a high-resolution TEM could also be used but ambiguities would remain in the interpretation of the origin of the image contrast. In order to overcome these problems of ambiguity, the annular dark field (ADF) image on a VG HB501 STEM was employed. Since this signal is proportional to mass thickness and Z3/2, we expected that the change in mass thickness locally associated with a cavity would be detectable in a thin enough region. These images show a clear correlation between features in the BF through-focus series which behave as cavities and features in the ADF image. This combination of imaging modes has provided convincing evidence for existence of the 1 nm cavities.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 183: Symposium E – High Resolution Electron Microscopy of Defects in Materials , 1990 , 231
Copyright
Copyright © Materials Research Society 1990

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References

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