Structure and stability of Σ3 grain boundaries in face centered cubic metals

Abstract

Σ3 grain boundaries form as a result of either growth twinning or deformation twinning in face centered cubic (fcc) metals and play a crucial role in determining the mechanical and electrical properties and microstructural stability. We studied the structure and stability of Σ3 grain boundaries (GBs) in fcc metals by using topological analysis and atomistic simulations. Atomistic simulations were performed for Cu and Al with empirical interatomic potentials to reveal the influence of stacking fault energy on the morphology of the twinned grains. Three sets of tilt Σ3 GBs were studied with respect to the tilt axis parallel to ⟨111⟩, ⟨112⟩, and ⟨110⟩, respectively. We showed that Σ3{111} and Σ3{112} GBs are thermodynamically stable and the others will dissociate into terraced interfaces regardless of the stacking fault energy. The morphology of the nano-twinned grains in Cu is predicted from the above analysis and found to match with experiments.

Keywords:

• grain boundary
• dislocation
• fcc metal
• atomistic simulation

Acknowledgments

This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. JW acknowledges the support provided by Los Alamos National Laboratory Directed Research and Development project ER20110573. We sincerely appreciate Prof. J. P. Hirth for his valuable comments.