Interfacial and mechanical characteristics of TiN/Al composites under nanoindentation

Abstract

This paper investigates the influence of the surface orientation of TiN and Al layers, as well as TiN layer thickness on the deformation behavior and mechanical characteristic of TiN/Al bilayer composites under the nanoindentation process through molecular dynamics (MD) simulation. The result shows that the TiN(111)/Al(111) workpiece with Ti-face has the greatest loading force and hardness, indicating that the strength of this specimen is improved better than other surface orientations, and the increase in TiN layer thickness leads to increase the loading force and hardness. However, defects such as dislocation and phase transformation appear also more in the TiN(111)/Al(111) workpiece with Ti-face, while the phase transformation and the number of dislocation in the Al layer are clearly decreased as increasing the TiN layer thickness. The surface morphology reveals that the sink-in phenomenon in indents has occurred in all samples with the change of TiN/Al surface orientations. Besides, the indents appear the sink-in for TiN layer thickness from 10 Å to 30 Å, and the pile-up is present in the indentation with TiN thicknesses of 50 Å and 70 Å. The atomic zone in the high stress–strain state is focused on the interface and around the indenter in all samples, and the interface acts as a barrier against the spread of stress and strain into the substrate interior. Furthermore, the atomic area in the high-temperature state is concentrated surrounding the indenter due to the friction between the substrate and indenter, and the deformation process of material from elastic to plastic causes the heat increase in the substrate