Molecular Dynamics Simulations Of Interaction Between Dislocations And Interfaces

Nanoscale multilayered composites often possess extraordinary mechanical properties interms of yield stress, ductility, and wear resistant. Now it has been widely used in aerospace,mechanical manufacturing, electronics, optical engineering and computer engineering fields.In the applied process of the thin film materials, people commonly focus on the reliability andservice life of the thin films. The binding property between the thin film and the substrate is akey indicator of metallic multilayers’ the reliability and service life, the interactionmechanisms between dislocations and interfaces dominate the binding properties of theinterfaces. Therefore, the interaction mechanism between dislocations and interfaces plays avital role in the field of the reliability and service life of the thin films.So it is an interestingand valuable thing to understand the interaction mechanisms between dislocations andinterfaces. With the development of high-performance computer, atomic simulations havebecome an effective method in the field of material properties forecast and design. In thepresent work, we have studied the interaction between dislocations and interfaces with3DMolecular Dynamic Simulations.Firstly, molecular dynamics simulations were carried out to investigate the nucleationand emission of dislocations from an interface in a bcc-Fe/Ni bilayer subjected to transverseloading. After relaxation, disordered types of dislocations were observed at both Fe(001)/Ni(001) and Fe(001)/Ni(111) interfaces, and rectangular dislocations types at Fe(001)/Ni(110) interface. The orientation effect on the mechanical properties of a Fe/Ni bilayersystem was investigated. The yield stress of the Fe(001)/Ni(110) system abtained is lowest.We also found that the yield stress of pure iron nanofilm was higher than that of a Fe/Nibilayer system, and the ductility was lower than that of a Fe/Ni bilayer system for giventemperature and strain rate. The simulation results obtained also show that the misfitdislocations at Fe/Ni interface acted as a source to nucleation and emission of glidedislocations. Glide dislocations nucleation and emission from misfit dislocation line at Fe/Niinterface. The existence of misfit dislocations and the lattice mismatch can also act as barriersto dislocation motion and transmission across the interface. More dislocations in Fe have beenarrested at the Fe/Ni interface, which provides sufficient stress for dislocations to transmitfrom Fe to Ni. Glide dislocations mainly occurred on {101} plane in Fe layer of FeNi bilayer,and {111} plane in Ni layer.Secondly, molecular dynamics simulations were carried out to study the mechanical properties of Cu(001)/Ni(001) interface boundaries with different twist angles subjected touniaxial loading. The results obtained revealed that square misfit dislocations networks can beobserved when the twist angle was lower than15.124, and the density of misfit dislocationsincreased with increasing twist angle. Face defects were formed when the twist angle washigher than15.124. It has been found that the interface configuration had a significant effecton the interface strength of the Cu/Ni system. The yield stress was found to decrease first withincreasing twist angle and it reached its lowest value at5.906twist angle. Subsequently, itincreased with increasing twist angle till it reached its highest value at15.124of the latter; itthen decreased again and finally became almost constant when the twist angle was larger thanapproximately20.