Atomistic modeling of the interaction of glide dislocations with “weak” interfaces

Using atomistic modeling and anisotropic elastic theory, the interaction of glide dislocations with interfaces in a model Cu–Nb system was explored. The incoherent Cu–Nb interfaces have relatively low shear strength and are referred to as “weak” interfaces. This work shows that such interfaces are very strong traps for glide dislocations and, thus, effective barriers for slip transmission. The key aspects of the glide dislocation–interface interactions are as follows. (i) The weak interface is readily sheared under the stress field of an impinging glide dislocation. (ii) The sheared interface generates an attractive force on the glide dislocation, leading to the absorption of dislocation in the interface. (iii) Upon entering the interface, the glide dislocation core readily spreads into an intricate pattern within the interface. Consequently, the glide dislocations in both Cu and Nb crystals are energetically favored to enter the interface when they are located within 1.5 nm from the interface. In addition to the trapping of dislocations in weak interfaces, this paper also discusses geometric factors such as the crystallographic discontinuity of slip systems across the Cu/Nb interfaces, which contribute to the difficulty of dislocation transmission across an interface. The implications of these findings to the unusually high strengths experimentally measured in Cu/Nb nanolayered composites are discussed.