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In-Situ TEM Studies of Sessile Dislocation Arrangements and N Vacancy Ordering in ZrN

Published online by Cambridge University Press:  15 February 2011

P. Li  and
J.M. Howe
P. Li
Affiliation:
Center for Solid State Science, Arizona State University, Tempe, AZ, 85287-1704, U.S.A
J.M. Howe
Affiliation:
Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904-4745, U.S.A.
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Abstract

Dissociation of perfect 1/2<110> single dislocations into two 1/6<112> Shockley partial dislocations in ZrN was observed by transmission electron microscopy (TEM). The 1/2<110> single dislocations have a super-jog character and are not coplanar with the dissociated Shockley partials. This sessile arrangement of dislocations may be responsible for the brittleness of ZrN. The wide separation of the partial dislocations bounding stacking faults indicates that the stacking-faults energy (SFE) is low in ZrN. The low SFE can be explained on the basis of a high vacancy concentration, which was confirmed by the appearance of diffuse intensity maxima in electron diffraction patterns due to short-range ordering (SRO) of N vacancies. In-situ heating experiments in the TEM revealed that the diffuse intensity maxima disappear during heating and reappear on cooling. This indicates that N (or N vacancy) diffusion scrambles the SRO arrangement of N vacancies during heating. The width of the stacking faults in ZrN increases with temperature, indicating that the SFE decreases as the vacancy concentration increases.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 779: Symposium W – Multiscale Phenomena in Materials - Experiments and Modeling Related to Mechanical Behavior , 2003 , W5.11
Copyright
Copyright © Materials Research Society 2003

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