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Yield Stress of Nano- and Micro- Multilayers

Published online by Cambridge University Press:  10 February 2011

P. M. Hazzledine  and
S. I. Rao
P. M. Hazzledine
Affiliation:
UES Inc., 4401 Dayton- Xenia Road, Dayton. OH 45432
S. I. Rao
Affiliation:
UES Inc., 4401 Dayton- Xenia Road, Dayton. OH 45432
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Abstract

An outline theory is given for the strengthening in polycrystalline and ‘single crystal’ multilayers. The model is based on the Hall-Petch theory applied to both the soft mode (in plane) and hard mode (cross plane) of deformation. In this theory the parameters to be evaluated are a Taylor factor M, the shear stress τ0 to move a dislocation within a multilayer and τ*, the shear stress needed to push a dislocation over a grain or interphase boundary. All three parameters are material- specific and attention is focussed on coherent multilayers of γ TiAl with micron thick layers and Cu-Ni with nanometer thick layers. M and some components of τ* are estimated classically. The remaining components of τ* and some components of τ0 are estimated from embedded atom simulations. The model captures the main experimental facts, that γTiAl is plastically very anisotropic with a rising yield stress as the lamellar thickness is refined and that Cu-Ni displays a peak in the yield stress at a layer thickness of approximately 10nm.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 434: Symposium U – Layered Materials for Structural Applications , 1996 , 135
Copyright
Copyright © Materials Research Society 1996

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