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Tem Investigation Of Precipitate Shapes And New Interface Phenomena In Al-Pb Alloys

Published online by Cambridge University Press:  02 July 2020

U. Dahmen  and
E. Johnson
U. Dahmen
Affiliation:
National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA94720
E. Johnson
Affiliation:
Ørsted Laboratory, University of Copenhagen, Universitetsparken 5, DK-2100Copenhagen, Denmark
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Extract

Transmission electron microscopy plays a key role in the investigation of precipitates and inclusions because it provides direct information at high spatial resolution, on their shape, orientation relationship, interface structure and composition.

This work has utilized high resolution and in-situ electron microscopy to study the equilibrium shapes and thermal behavior of Pb precipitates in Al. It was found that PB precipitates within Al grains form in parallel-cube orientation relationship, are cuboctahedral in shape, adopt a sequence of magic sizes, and display an increase in aspect ratio with decreasing size. These observations have been explained in terms of interfacial energy and residual strain energy.

When the same Pb precipitates form on grain boundaries, their shapes are significantly different. This is apparent from figure 1 which shows a 90° <110> tilt grain boundary in Al with a small cuboctahedral Pb precipitate in the upper grain and a large complex-shaped Pb particle on the grain boundary.

Type
Atomic Structure And Microchemistry Of Interfaces
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 134 - 135
Copyright
Copyright © Microscopy Society of America

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References

1.Dahmen, U., Xiao, S.Q., Paciornik, S., Johnson, E. and Johansen, A., Phys. Rev. Lett. 78 (1997) 471CrossRefGoogle Scholar
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4.This work is supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under Contract No. DEAC03-76SF00098Google Scholar