Journal
ACTA MATERIALIA
Volume 56, Issue 17, Pages 4762-4770Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2008.05.030
Keywords
Plastic deformation; Yield phenomena; Crystal plasticity; Size dependence; Mechanical properties
Funding
- US Department of Energy: Division of Materials Sciences and Engineering
- Office of FreedomCAR and Vehicle Technologies
- Office of Science
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A NiAl-Mo eutectic was directionally solidified to produce composites with well-aligned single-crystal Mo-alloy fibers embedded in a NiAl matrix. They were pre-strained by compressing along the fiber axis and then the matrix was etched away to expose free-standing micropillars having different sizes (360-1400 nm) and different amounts of pre-strain (0-11%). Compression testing of the pillars revealed a variety of behaviors. At one extreme were the as-grown pillars (0%, pre-strain) which behaved like dislocation-free materials. with yield stresses approaching the theoretical strength, independent of pillar size. At the other extreme were pillars pre-strained 11%, which behaved like the bulk, with reproducible stress-strain curves, relatively low yield strengths, stable work-hardening and no size dependence. At intermediate pre-strains (4-8%), the stress-strain curves were stochastic and exhibited considerable scatter in strength. This scatter decreased with increasing pre-strain and pillar size, suggesting a transition front discrete to collective dislocation behavior. (C) 2008 Acta Materialia lnc. Published by Elsevier Ltd. All rights reserved.
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