Mechanism Analysis of Mechanical Properties for Cu-Ni Bilayers with Semi-Coherent Interface: A Molecular Simulation

Due to the influence of interface lattice mismatch, nano metal multilayers with different interface structures can be prepared in the alternate deposition process. However, the difference of interface structure often has an extremely important influence on the mechanical properties of nano indentation. Therefore, in this paper, the significant difference of mechanical properties between Cu based Ni film and Ni based Cu film semi-coherent interface structure was analyzed, and the interaction law of interface structure and dislocation induced by indentation was revealed. It was found that the different interface structures in the Cu/Ni bilayer film significantly affected the mechanical properties of the material. Among them, the existence of the semi-coherent interface of the Cu/Ni bilayer film can repel the movable dislocations produced in the indentation by the mismatched dislocation network on the semi-coherent interface of the Cu based Ni film, and so it was advantageous for the dislocation to penetrate the semi-coherent region into the copper film, which can be turned into strengthening effect externally.The mismatch dislocation network on the semi-coherent interface of Ni based Cu film had an attractive effect on the movable dislocations produced in the indentation, so that the dislocation was prevented from penetrating the semi-coherent region into the nickel film, which was shown as softening effect externally and can enhance the toughness of the material. In addition, the theoretical formula of mirror force between different moduli proposed by Koehler can be used to describe the significant difference. The research results will play a very practical guiding significance and theoretical reference value for the application of nano multilayers as coatings in MEMS, surface protection and wear resistance of marine equipment, aerospace and other fields.