The effect of interfacial imperfections on plastic deformation in nanoscale metallic multilayer composites

Nanoscale metallic multilayer (NMM) composites represent a class of advanced engineering materials that are shown to exhibit high structural stability, mechanical strength, high ductility, toughness and resistance to fracture and fatigue. This paper addresses the question of the effect of the interface imperfections on the strengthening of NMMs with incoherent interfaces, by performing molecular dynamics simulations. Two types of interfaces are considered, a perfect one, and one with discontinuities (steps and ledges). Our simulations demonstrate that the result of the interaction between dislocations and interfaces is the creation of interfacial disconnections made of a dislocation that spreads within the interface, and a step entrapped at the interface. The energy calculations show that these steps increase the total energy of the system and enhance the strengthening effect of the interface by adding extra barriers to slip transmission, thus improving the mechanical properties of the structure.