A Molecular Dynamics Study on the Structures of Low-Angle [001] Tilt Boundaries in Copper

Abstract

The purpose of the present study is to investigate the grain boundary (GB) structures of low angle [001] symmetrical tilt boundaries by means of the molecular dynamics (MD) simulations. The misorientation angles θ of the model copper bicrystals were set from 2.9° to 14.3° ({100} GB plane) and from 64.0° to 86.1° ({110} GB plane). The misorientation angles θ ranged from 64.0° to 86.1° correspond to the deviation angle Δθ from 3.9° to 26.0°, where the Δθ is a deviation angle from the single crystal state. After the relaxation at GBs by the MD calculation, it was recognized that some low-angle GBs were composed from arrays of a/2 ‹110› lattice dislocations as predicted from the widelyknown dislocation array model of a low angle GB. The GB structures of the {110} boundary plane were the arrays of a/2 [110] dislocations. On the other hand, a/2 [110] and a/2 [110] dislocations were alternately arranged along the {100} GB. The GBs with large deviation angles from a single crystal state contained another structure that is different from the a/2 ‹110› dislocation. The ranges of the deviation angle where the GBs are represented exclusively by the a/2 ‹110› dislocations depended strongly on the geometry of the GB plane. The critical deviation angles Δθ_c for the {100} and {110} GB planes were 8.8° and 22.6°, respectively. The average distances between the dislocations in these boundaries were sensitive to both the misorientation angle and the GB plane. The average dislocation distances obtained at the MD simulations agreed with those calculated from the dislocation array model of a low angle boundary with a good accuracy.