Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 546, Issue -, Pages 248-257Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2012.03.061
Keywords
Shear deformation; Activation volume; Strain-hardening rate; Nanocrystalline metals; Plasticity
Categories
Funding
- German Science Foundation [DFG-FOR714]
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Nanocrystalline Pd90Au10 (grain size <10 nm) has been deformed under dominant shear and superimposed compression to large plastic strains (epsilon> 20%). Taking stress strain curves at different strain rates (10(-4) < epsilon < 10(0)) allowed us to extract the shear activation volume and strain rate sensitivity as a function of plastic strain, which are of the order of 4b(3) and 0.035, respectively. Particularly, the plastic strain-dependent shear activation volume evolves through a maximum value, which relates to yielding. Analyzing the strain hardening rate Theta as a function of applied stress enables to determine strain rate dependent macroyield stresses. Scaling of the applied stress with the macroyield stress yields in addition also the strain rate dependent onset stresses of microyield. Surprisingly, strain hardening associated with interfacial deformation modes dominates the stage of microplasticity, whereas, in the macroplastic regime the strain hardening rate saturates at strains >10% to approach a more or less generic value of Theta/G = 0.015. (C) 2012 Elsevier B.V. All rights reserved.
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