Molecular Dynamics Simulation Of The Effect Of Temperature And Layer Thickness On The Tensile Property Of Cu/Al Nanoscale Film

Cu/Al film has the advantages of high strength,corrosion resistance and good thermal conductivity,and it has been widely used in micro/nano electromechanical systems and aerospace.The study of mechanical properties of Cu/Al film has important theoretical guiding significance to its practical application.In this paper,molecular dynamics method is used to study the effect of temperature and holding time on the interface diffusion and mechanical properties of Cu/Al film.At the same time,this paper also study the mechanical properties of Cu/Al double layer and multilayer film and plastic deformation behavior at atomic scale.The research content of this paper is mainly from the following parts:(1)The influence of holding temperature and holding time on the interface diffusion and mechanical properties of Cu/Al film and effect of tensile temperature on mechanical properties of Cu/Al film are studied.The results indicate that the number of Cu atom diffusing into Al film is larger than Al atom diffusing into Cu film.Cu atom diffuses into the depths of Al film and Al atom only diffuses in the interface.Diffusion coefficient of Al atom is larger than Cu atom.The diffusion of Cu atom and Al atom is not obvious at lower temperatures and diffusion is better under the temperature of 800 K.With holding time increasing,the thickness of interface region increases and then remains unchanged basically.The holding time should not be too long or too short.When holding time is 1.2 ns,Cu/Al film achieves the best mechanical properties.The tensile temperature could affect the mechanical properties of Cu/Al film,and the yield strength increases with the decrease of tensile temperature.(2)The research results of uniaxial tensile of Cu/Al bilayer show that: As the thickness decreases,the yield strength increases first and then decreases and the critical dimension of yield strength is 7 nm.In addition,we research the plastic deformation behavior of Cu/Al bilayer of different thickness.The results indicate that: With the thickness of Cu/Al double bilayer shorter than 7 nm,the main formation of Al layer and Cu layer is intrinsic stacking fault in the process of plastic deformation.When the thickness of Cu/Al bilayer reaches to critical length(here 7 nm),the main formation of Al layer is twinning,and the main formation of Cu layer is a complex stacking structure,which obviously improves the strength of the film.When the thickness of the Cu/Al bilayer increases to 17 nm,the main formation of Al layer is the intrinsic stacking fault,and the main formation of Cu layer is the four-layer hexagonal close-packed structure.Besides,with the decrease of the thickness of the Cu/Al bilayer,the stair-rod density first changes smoothly and then increases rapidly and then decreases.When the thickness of Cu/Al bilayer reaches to critical point(here 7 nm),the stair-rod density reaches to the maximum.(3)The results of tensile study of Cu/Al multilayer show that: The yield stress of Cu/Al multilayer shows obvious size effect.With the increase of Cu/Al multilayer thickness,the yield strength shows a trend of increasing and then decreasing.In addition,the dislocation evolution process of Cu/Al multilayer during plastic deformation is studied.It is found that the main deformation of Cu/Al multilayer is the intrinsic stacking fault and twin.The stair-rod number of the Cu/Al multilayer with a thickness of 10 nm reaches to the maximum,which quantitatively verifies the simulation result that the yield strength of the Cu/Al multilayer with thickness of 10 nm reaches the maximum.