Mechanical Effect Of Interface Dislocations In Layered Micro-Nanostructure Metallic Material

Layered micro-nanostructure metallic material has high strength,good shock resistance and radiation resistance.Besides,it also has good resistance to wear,corrosion and high temperature.Layered micro-nanostructure material can be made up of different layer materials,which provides a good chance to improve the mechanical properties,thermal properties,optical properties and magnetic properties by adjusting them.Due to the advantages of layered micro-nanostructure metallic material,it has been widely used in mechanics,optics,electronics,energy and other fields.In layered micro-nanostructure metallic materials,the interfaces,interface dislocations and layer thickness often play an important role in determing the mechanical properties.In this work,we investigated the effects of core spreading of interface dislocations on the elastic field in bimaterials and interface dislocation arrays on the strength of layered micro-nanostructure materials,the size effect of layer thickness and the commensurate dichromatic pattern(CDP)of coherent interfaces.The obtained results are as follows:Based on the complexity and diversity of dislocation core spreading,three simple dislocation core spreading models were proposed to describe the distribution of Burgers vectors in spreading region,i.e.uniform distribution model,linear distribution model and cosine distribution model.Based on the results of conventional compact dislocation model and Stroh formalism,the elastic fields due to previous three dislocation core-spreading models are respectively derived in bicrystal materials for the first time.Furthermore,we presented a multi-segment linear distribution model to improve the accuracy in describing the actual distribution of the spreading Burgers vectors.By neglecting the stiffness mismatch of the materials,we derived the elastic fields due to interface core-spreading dislocation arrays in multilayered micro-nanostructure materials.The reliability of the theoretical expressions is verified by numerical analyses on the Cu-Nb multilayered nanomaterials.The effects of the width of core-spreading region,the period length of dislocation arrays,the layer thickness and the number of layers on the mechanical properties are all explored.It shows the mechanical properties will be strengthened with increasing the width of core-spreading region and decreasing the period length of dislocation arrays.Regardingthe influence of layer thickness on mechanical properties,for the first time,a critical value of layer thickness was determined from the perspective of theoretical simulation.In other words,the material will be strengthened with decreasing layer thickness when layer thickness is larger than the critical,whereas the material will be weakened with decreasing layer thickness when layer thickness is smaller than the critical.Particularly,the critical layer thickness obtained by theoretical simulation is in good agreement with previous reported experimental results.From the perspective of lattice geometric match and physical mechanical equilibrium,three different typical interfaces were selected to investigate interface CDP configurations.According to the results,the interface CDP configuration can be uniquely determined in isotropic bimaterials.However,the interface CDP configuration of anisotropic bimaterial will be affected by interface dislocation types and arrangements.Besides,the selection of interface reference lattice constant will influence the accurate prediction of the magnitude of Burgers vector of interface dislocation and consequently mechanical properties.