Strength and tension/compression asymmetry in nanostructured and ultrafine-grain metals
Document Type
Article
Publication Date
9-3-2003
Abstract
The recent literature is reviewed with respect to the strength-limiting deformation mechanisms in nanocrystalline and ultrafine-grain metals. Based on these results, a deformation mechanism map is proposed for FCC metals with ultrafine-grain sizes. In the absence of flaw-controlled brittle fracture, it is concluded that the strength-limiting mechanism in metals with grain sizes between approximately 10 and 500-1000 nm is dislocation emission from grain boundary sources. A simple model for the strength in this regime of grain sizes is developed from classical dislocation theory, based on the bow-out of a dislocation from a grain boundary dislocation source. The model predicts not only the strength as a function of grain size, but also the observed tension/compression asymmetry of the yield strength. The tension/compression asymmetry arises from the pressure dependence of the dislocation self-energy during bow-out. The pressure dependence is a function of material and grain size, consistent with experimental observations. Finally, the model provides a physical basis for a pressure-dependent yield criterion. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Publication Title
Acta Materialia
Recommended Citation
Cheng, S.,
Spencer, J.,
&
Milligan, W.
(2003).
Strength and tension/compression asymmetry in nanostructured and ultrafine-grain metals.
Acta Materialia,
51(15), 4505-4518.
http://doi.org/10.1016/S1359-6454(03)00286-6
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/7677