Size dependence for mechanical properties of Ti/Cu multilayered nanowire with a semi-coherent interface

Abstract

Metallic multilayered nanowires have a wide application prospect in micro-nano devices because of their superior physical and chemical properties and microstructure designability. Size effects on the tensile behaviors of Ti/Cu multilayered nanowires are investigated by molecular dynamic simulations. Aspect ratios of 1:4, 1:3, 1:2, 1:1, 1:0.75, and 1:0.67 and sectional dimensions of 3, 4, 5, 6, and 7 nm are adopted to construct nanowires with different sizes. Simulation results indicate that the strength of Ti/Cu nanowires decreases with the decrease of aspect ratio in the large aspect ratio range (>1:2) and all simulated sectional dimension ranges, showing a reverse Hall-Petch effect. The Hall-Petch law can only be satisfied in a small aspect ratio range (<1:2). Deformation mechanism transition is found in the critical aspect ratio of 1:2. When the aspect ratio is larger than 1:2, crystalline phases of Ti and Cu layers dominate the plastic deformation of Ti/Cu nanowires. Crystal phases and interface both bear plastic deformation when the aspect ratio is smaller than 1:2. Interface is an important factor in the strength and deformation of Ti/Cu nanowires. The variation of interface fraction and interaction between interface and dislocation motion determine the tendency of strength variation for Ti/Cu nanowires.