Energy of low angle grain boundaries based on continuum dislocation structure

TL;DR

This paper introduces a continuum dislocation-based model to accurately predict the energy and structure of low angle grain boundaries in fcc aluminum, capturing anisotropic effects and matching atomistic simulation results.

Contribution

The novel continuum model efficiently computes low angle grain boundary energies for arbitrary orientations using dislocation networks constrained by Frank's formula.

Findings

Accurately predicts grain boundary energies and dislocation densities.

Shows excellent agreement with atomistic simulation results.

Applicable to various boundary orientations and Burgers vectors.

Abstract

In this paper, we present a continuum model to compute the energy of low angle grain boundaries for any given degrees of freedom (arbitrary rotation axis, rotation angle and boundary plane orientation) based on a continuum dislocation structure. In our continuum model, we minimize the grain boundary energy associated with the dislocation structure subject to the constraint of Frank's formula for dislocations with all possible Burgers vectors. This constrained minimization problem is solved by the penalty method by which it is turned into an unconstrained minimization problem. The grain boundary dislocation structure is approximated by a network of straight dislocations that predicts the energy and dislocation densities of the grain boundaries. The grain boundary energy based on the calculated dislocation structure is able to incorporate its anisotropic nature. We use our continuum model to systematically study the energy of $<111>$ low angle grain boundaries in fcc Al with any boundary plane orientation and all six possible Burgers vectors. Comparisons with results of the atomistic simulations show that our continuum model is able to give excellent predictions of the energy and dislocation densities of low angle grain boundaries. We also study the energy of low angle grain boundaries in fcc Al with varying rotation axis while the rest degrees of freedom are fixed. With minor modifications, our model can also apply to dislocation structures and energy of heterogeneous interfaces.