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Plastic Deformation Mechanisms in Nanocrystalline Columnar Grain Structures by Diana Farkas; William A. Curtin is a Engineering article available to read on EtoBox.

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We present an atomistic study of the plastic deformation mechanisms occurring in columnar structures of nanocrystalline Ni, with particular emphasis on the process of dislocation emission form the grain boundaries. The samples are constructed with grain boundaries characterized by random tilt misorientations around a common 1 1 0 type axis. All samples contain the same 36 grains polycrystalline microstructure, with grain sizes ranging from 4 to 20 nm in order to isolate size effects on the deformation mechanisms. Tensile deformations up to 8% were simulated and the strain stress curves observed for these samples show grain size effects in both the elastic and plastic portions. An inverse Hall-Petch effect is observed for the nominal stress at a fixed strain, but disappears when the grain size-dependent elastic modulus is used to construct an 0.5% offset yield stress. Both dislocation emission from the grain boundaries and grain boundary accommodation of plasticity are observed. Dislocation emission comes largely from pre-existing dislocation-like structures in the grain boundaries, and increases rapidly for grain sizes >4 nm. However, the number of dislocations per unit length of g

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Author

Diana Farkas; William A. Curtin

Publisher

Elsevier Science; Elsevier ; Elsevier BV (ISSN 0921-5093)

Published

2005

Language

EN

Field

Engineering (Physical Sciences)