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Pile-Up Based Hall-Petch Considerations at Ultra-Fine Grain Sizes

Published online by Cambridge University Press:  15 February 2011

T. R. Smith
Affiliation:
Materials and Nuclear Engineering Department
R. W. Armstrong
Affiliation:
Department of Mechanical Engineering, University of Maryland, College Park, MD 20742
P. M. Hazzledinew
Affiliation:
UES Inc., 4401 Dayton-Xenia Road, Dayton OH 45432
R. A. Masumura
Affiliation:
Naval Research Laboratory, Washington DC 20375-5343
C. S. Pande
Affiliation:
Naval Research Laboratory, Washington DC 20375-5343
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Abstract

The dislocation pile-up explanation for the Hall-Petch (H-P) relation is re-examined for ultrafine grain sizes when only a few dislocations are involved in the pile-up, formed necessarily at applied stress levels near to the theoretical limit. Each dislocation added to the pile-up produces a step reduction in the H-P stress. Consequently, differences in dislocation configurations and types of pile-ups are easily recognized in the limit of small dislocation numbers. A significant reduction occurs in the H-P slope value (i.e., microstructural stress intensity) for the extreme case of only one dislocation loop being expanded against the grain boundary obstacle stress.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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