Mechanical and tribological properties of Ni/Al multilayers-A molecular dynamics study

Mechanical and tribological properties of multilayers with nanometer thickness are strongly affected by interfaces formed due to mismatch of lattice parameters. In this study, molecular dynamics (MD) simulations of nanoindentation and following nanoscratching processes are performed to investigate the mechanical and tribological properties of Ni/Al multilayers with semi-coherent interface. The results show that the indentation hardness of Ni/Al multilayers is larger than pure Ni thin film, and the significant strength of Ni/Al multilayers is caused by the semi-coherent interface which acts as a barrier to glide of dislocations during nanoindentation process. The confinement of plastic deformation by the interface during nanoscratching on Ni/Al multilayers leads to smaller friction coefficient than pure Ni thin film. Dislocation evolution, interaction between gliding dislocations and interface, variations of indentation hardness and friction coefficient are studied.