# American Institute of Mathematical Sciences

October  2018, 23(8): 2989-3021. doi: 10.3934/dcdsb.2017183

## Stability of dislocation networks of low angle grain boundaries using a continuum energy formulation

 1 Department of Mathematics, Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong 2 Department of Mathematics, University of Connecticut 341 Mansfield Road, Storrs, CT 06269, USA

Received  June 2016 Revised  June 2017 Published  July 2017

Fund Project: The first author is partially supported by the Hong Kong Research Grants Council General Research Fund 606313. The second author thanks HKUST for hospitality

Low angle grain boundaries can be modeled as arrays of line defects (dislocations) in crystalline materials. The classical continuum models for energetics and dynamics of curved grain boundaries are mainly based on those with equilibrium dislocation structures without the long-range elastic interaction, leading to a capillary force proportional to the local curvature of the grain boundary. The new continuum model recently derived by Zhu and Xiang (J. Mech. Phys. Solids, 69,175-194,2014) incorporates both the long-range dislocation interaction energy and the local dislocation line energy, and enables the study of low angle grain boundaries with non-equilibrium dislocation structures that involves the long-range elastic interaction. Using this new energy formulation, we show that the orthogonal network of two arrays of screw dislocations on a planar twist low angle grain boundary is always stable subject to both perturbations of the constituent dislocations within the grain boundary and the perturbations of the grain boundary itself.

Citation: Yang Xiang, Xiaodong Yan. Stability of dislocation networks of low angle grain boundaries using a continuum energy formulation. Discrete & Continuous Dynamical Systems - B, 2018, 23 (8) : 2989-3021. doi: 10.3934/dcdsb.2017183
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##### References:
(a) Schematic illustration of a twist boundary. (b) Dislocation network consisting of two orthogonally intersecting screw dislocation arrays on a low angle twist boundary. For this twist boundary, across each horizontal dislocation (with Burgers vector $\mathbf b_1$) in the upper grain, the atoms above it shift to the left by $b_1/2$ and those below it shift to the right by $b_1/2$ with respect to the lower grain; across each vertical dislocation (with Burgers vector $\mathbf b_2$) in the upper grain, the atoms on its left shift downward by $b_2/2$ and those on its right shift upward by $b_2/2$ with respect to the lower grain. The net effect is making the upper grain rotate in the counterclockwise direction with respect to the lower grain
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