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Analysis of grain boundary effect of bulk polycrystalline materials through nanomechanical characterization

T Ohmura and K Tsuzaki

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Indentation-induced deformation behaviour was characterized in nano-scale for bulk polycrystalline materials to understand strengthening factors of macroscopic properties especially for the grain boundary effect. Compared with deformation behaviour in the vicinity of single grain boundary and grain interior of an interstitial free steel, plasticity initiation occurs at a lower applied stress near the grain boundary, which means the grain boundary is an effective dislocation source. The subsequent deformation after plasticity initiation is affected by the grain boundary as a barrier to dislocation motion. Strengthening factors of matrix and grain boundaries were evaluated separately for the Fe–C tempered martensite. The contribution of grain boundaries depends on the morphology of precipitates on grain boundaries. Combining the dislocation pile-up model and the Hall–Petch relation, the existence of the film-like carbide on the grain boundary remarkably affects the locking parameter k.


PACS

61.72.Mm Grain and twin boundaries

61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

61.72.J- Point defects and defect clusters

62.20.F- Deformation and plasticity

81.40.Lm Deformation, plasticity, and creep

62.25.-g Mechanical properties of nanoscale systems

Subjects

Nanoscale science and low-D systems

Condensed matter: structural, mechanical & thermal

Dates

Issue 7 (7 April 2008)

Received 6 August 2007, in final form 14 December 2007

Published 12 March 2008



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