On the elastic tensile deformation of 〈1 0 0〉 bicrystal interfaces in copper

The elastic response of 〈1 0 0〉 tilt bicrystal copper interfaces, when subjected to a uniaxial tensile deformation applied normal to the boundary, is examined using molecular dynamics simulations with an embedded-atom method potential. Simulations in this work are designed explicitly to study the discrete atomic motions that occur within the grain boundary region prior to dislocation nucleation. Seven symmetric tilt interfaces with low-order coincident site lattice descriptions are considered: Σ5 (2 1 0), Σ5 (3 1 0), Σ13 (3 2 0), Σ13 (5 1 0), Σ17 (4 1 0), Σ17 (5 3 0) and Σ29 (7 3 0). Simulations indicate that bicrystal boundaries which contain the C structural unit deform via an elastic structural transition which initiates at a critical threshold stress. Furthermore, it is found that the excess interfacial energy decreases during elastic deformation for both Σ5 and Σ29 interfaces, whereas it increases for the Σ13 and Σ17 boundaries. It is suggested that this observation can be attributed to the geometric constraints imposed by the structural units that comprise the Σ5 and Σ29 tilt boundaries, which has significant implications for grain boundary engineering and continuum models of elastic and viscoplastic deformation in nanocrystalline materials.