Article ID Journal Published Year Pages File Type
1450024 Acta Materialia 2008 9 Pages PDF
Abstract

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 from discrete to collective dislocation behavior.

Related Topics
Physical Sciences and Engineering Materials Science Ceramics and Composites
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