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In polycrystals, grain boundaries (GBs) are widely accepted as potential diffusion pathways and crack-initiation sites. GBs always form network structures in three-dimensional (3D) materials including regular GB planes, triple junctions (TJs), and high-order junctions (HJs), and thus the influence of these components on the mechanical behavior of polycrystals should be understood. In this study, we used molecular dynamics (MD) simulations combined with a new on-the-fly GB component identification method to investigate dynamic behaviors such as atomic diffusion and nanovoid formation under uniaxial tensile loading in body-centered cubic (bcc)-Fe polycrystals. Our results show that the local atomic diffusion ability of the HJ is the highest among the GB components, followed by those of the TJ and GB. Uniaxial tensile loading simulation results suggest that junction-rich regions containing multiple HJs and TJs act as hotspots for nanovoid formation. Stress concentration at HJs provides the driving force for vacancy/nanovoid formation, and high atomic diffusivities of TJs and HJs facilitate vacancy transport and aggregation. The obtained results for the atomic diffusion ability and nanovoid formation of the GB components are comparable to previous experimental observations. The present study contributes to a deeper, fundamental understanding of the mechanical behavior of 3D GB networks and highlights the GB network topology as an important factor in controlling the mechanical properties of nanopolycrystals.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Molecular dynamics, Polycrystal, Grain-boundary junctions, Dynamic behaviors, Three-dimensional grain boundary network

Date published: 2026-08-06

Publisher: Elsevier BV

Journal:

• Acta Materialia (ISSN: 13596454) vol. 318 122624

Funding:

• Government of Japan Ministry of Education Culture Sports Science and Technology JPMXP1122684766
• Japan Society for the Promotion of Science 26H02202
• Japan Society for the Promotion of Science 24H00389

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1016/j.actamat.2026.122624

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Updated at: 2026-10-28 13:13:27 +0900

Published on MDR: 2026-10-28 14:27:12 +0900