半共格界面铜镍双层膜力学差异机制纳观探析

为深入了解纳米金属多层膜在沉积法交替制备中, 因晶格失配制备出不同半共格界面的金属多层膜受载诱导的力学特性差异的机制，本文作者基于经典力学的分子动力学法，对半共格Cu基Ni膜和Ni基Cu膜两种界面结构的力学性能展开探析，揭示出多层膜半共格界面失配位错网与压痕诱导产生可动位错的相互作用规律. 研究发现: 铜镍双层膜半共格界面结构可有效提升力学性能，归因于铜镍半共格界面受载产生的柏氏矢量Shockley分位错的差异. Cu基Ni膜半共格界面上的失配位错网对压痕中产生的可动位错表现为排斥，有利于位错穿透半共格区域进入铜基中，对外表现为强化作用；Ni基Cu膜半共格界面上的失配位错网对压痕中产生的可动位错表现为吸引，阻碍位错穿透半共格区域进入镍基中，对外表现为软化作用，增强了材料抵抗变形的能力、耐磨性和韧性. 该性质差异可用Koehler提出的两种不同材料模量间镜像力理论解释. 此研究结果对铜镍多层膜作为涂层应用于微机电系统、海洋装备和航空航天等重大战略领域有着重要理论指导意义与借鉴价值. 

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.