Void growth via atomistic simulation: will the formation of shear loops still grow a void under different thermo-mechanical constraints?

Abstract

Molecular dynamics (MD) simulations under different mechanical and thermal constraints are carried out with a nanovoid embedded inside a single-crystal, face-centred-cubic copper. The dislocation emission angles measured from MD plots under 0.1 K, uniaxial-strain simulation are in line with the theoretical model. The dislocation density calculated from simulation is qualitatively consistent with the experimental measurement in terms of a saturation feature. The ‘relatively farthest-travelled’ atoms are employed to reflect the correlation between the dislocation structure and the void growth. At a smaller scale, the incomplete shear dislocation loops on the slip plane contribute to the local material transport. At a larger scale, the dislocation structures formed by those incomplete shear loops further facilitate the growth of nanovoid. Compared to the uniaxial-strain case, the void growth under the uniaxial-stress is very limited. The uniaxial-strain loading results in an octahedron void shape. The uniaxial-stress loading turns the nanovoid into a prolate ellipsoid along the loading direction. In the simulation, the largest specimen contains 12 million atoms and the lowest strain rate applied is 2 × 10⁶ s⁻¹. Under all the different thermomechanical constraints concerned, the formation of incomplete shear dislocation loops are found capable of growing the void.

Keywords:

• Void growth mechanism
• Nosé–Hoover method
• MD simulation
• nanovoids
• dislocation emission

Acknowledgement

We acknowledge the computing resources and technical support from the Western Canada Research Grid (WestGrid). The helpful and enlightening discussion with Prof. Tian Tang at University of Alberta is gratefully appreciated.

Notes

1. See the minimise command in the LAMMPS manual (28 Jun 2014 version).

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), and is gratefully acknowledged.