Molecular dynamics modeling of self-diffusion along a triple junction

TL;DR

This study uses molecular dynamics to model self-diffusion along a triple junction in copper, revealing that while TJs are faster than general grain boundaries, their contribution to high-temperature creep may be limited.

Contribution

We developed a computational method to create stable triple junctions with controlled misorientations and analyzed their diffusion properties in copper.

Findings

TJ diffusion is only twice as fast as Σ5 grain boundary diffusion.

Both TJs and GBs exhibit premelting behavior near melting point.

Differences in diffusivity may not significantly impact high-temperature creep.

Abstract

We propose a computational procedure for creating a stable equilibrium triple junction (TJ) with controlled grain misorientations. We apply this procedure to construct a TJ between a {\Sigma}5(210) grain boundary (GB) and two general high-angle GBs in copper, and calculate the diffusion coefficients along the TJ and the GBs using molecular dynamics with an embedded-atom potential. The TJ diffusion is only a factor of two faster than diffusion in the {\Sigma}5 GB but significantly faster than diffusion in the general GBs. Both the GBs and the TJ studied here show a premelting behavior near the bulk melting point, where their diffusivities converge to the diffusivity of bulk liquid. Although our results are consistent with the common assumption that TJ diffusion is generally faster than GB diffusion, the difference between the two diffusivities does not appear to be large enough to ensure a significant contribution of TJs to diffusional creep in polycrystals at high temperatures.