Interplay between sample size and grain size: Single crystalline vs. ultrafine-grained chromium micropillars

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:674

Article

Fritz, R.¹  Maier-Kiener, V.²  Lutz, D.¹  Kiener, D.¹ 

[1] Univ Leoben, Dept Mat Phys, Leoben, Austria

[2] Univ Leoben, Dept Phys Met & Mat Testing, Leoben, Austria

关键词: Micromechanics;    Crystal plasticity;    Size effect;    Bcc;    Ultrafine-grained;    In-situ SEM;   

DOI  :  10.1016/j.msea.2016.08.015

来源: Elsevier

【 摘 要 】

To gain insights into the influence of the microstructure on the strengthening behaviour in confined volumes, single crystalline (sxx) and ultrafine-grained (ufg) Cr micropillars were investigated using in-situ scanning electron microscope microcompression tests. Post-compression images of the sxx pillars indicate crystallographic slip, while the ufg pillars reveal a bulk-like deformation behaviour and an emergence of grains from the sample surface. Stress-strain curves of sxx samples show intermittent flow and a scaling behaviour agreeing well with other bcc metals investigated previously. Also for ufg samples a size-dependent strength with a reduced but non-negligible scaling exponent is determined. This latter ufg size effect contributes to an increasing influence of near-surface grains controlling plastic flow with decreasing pillar diameter. While for micron-sized pillars the strength differs between the two microstructures, the two scaling trends converge for sub-micron pillars with diameters close to the grain size, indicative of a transition from boundary-mediated to single crystal plasticity. (C) 2016 The Authors. Published by Elsevier B.V.

【 授权许可】

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