Abstract
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Grain boundaries (GBs) can play a role as the favored locations to annihilate point
defects, such as interstitial atoms and vacancies. It is thus highly probable that
different boundary structures can be simultaneously present in equilibrium with each
other in the same GB, and thus the GB achieves a metastable state. However, the
structural transition and deformation mechanism of such GBs are currently not well
understood. In this work, molecular dynamics simulations were carried out to study
the multiple structures of a Σ5(310)/[001] GB in bicrystal Al and to investigate the
effect of structural multiplicity on the mechanical and kinetic properties of such a
GB. Different GB structures were obtained by changing the starting atomic configuration
of the bicrystal model, and the GB structures had significantly different
atomic density. For the Σ5(310) GB with metastable structures, GB sliding was the
dominant mechanism at a low temperature (T=10K) under shear stress. The
sliding mechanism resulted from the uncoordinated transformation of the inhomogeneous
structural units. The nucleation of voids was observed during GB
sliding at the low temperature, and the voids subsequently evolved to a nanocrack at
the boundary plane. Increasing the temperature can induce the structural transition of
local GB structures and can change their overall kinetic properties. GB migration
with occasional GB sliding dominated the deformation mechanism at elevated
temperatures (T=300 and 600 K), and the migration process of the metastable GB
structures is closely related to the thermally assisted diffusion mechanism.