The Evolution Of Dislocation Network And Mechanical Properties Of Ni-based Single Crystal Superalloys

Ni-based single-crystal superalloys have been widely used as crucial materials for turbine blades in aeroengines due to their high temperature superior mechanical properties.oxidation resistance and thermal corrosion resistance.A lot of experimental research has 'been observed that the ?/?' phase interface of the Ni-based single-crystal superalloys will generate dislocation network structure under temperatures and loading conditions,the formation and role of the interfacial dislocation networks had a cdose relationship with high temperature mechanical properties of alloys.So studying the formation and evolution of the dislocation network has an important theoretical and practical significance.But it is difficult to observe real-time evolution of nickel-based single crystal dislocation network through experiment,on the other hand,the process of formation and evolution of the dislocation network and interface dislocation motion remain to be further discussed.In this paper,molecular dynamics simulations are used to study the evolution of the dislocation network and mechanical properties of Ni-based single-crystal superalloys under different temperature and loading.Meanwhile,the influence of the temperature,load,strain rate and orientation on interface dislocation network morphology,damage evolution characteristics and relevant mechanical properties are also been discussed.The main contents and results include:(1)The[001]orientation of nickel base single crystal superalloy interface dislocation network structure are simulated,the influence of mismatch degree on the model and temperature on the dislocation network structure are analyzed.From the simulation we can find the dislocation network structure of[001]orientation is mosic structure after relaxation.Significant changes have taken place in the size of the model under different mismatch degree,but the shape of the dislocation network and the evolution process are not affected.With a higher temperature,the model of the initial stress value is higher,and the dislocation network are more likely to create deformation damage.When stress value exceeds the critical stress value,dislocation will move in the direction of the a/2[110]to pile up.(2)The evolution of misfit dislocation network at ?/?' phase interface and tensile mechanical properties of[001]orientation Ni-based single crystal superalloys at different temperatures and strain rates are studied using molecular dynamics(MD)simulations.The results show that the dislocation networks can not only stabilize and strengthen the interface,but also enhance the creep resistance through preventing the matrix dislocation from cutting into the ?' precipitate.The temperature has influence on the elastic modulus of material,as well as the dislocation network structural integrity of the alloy largely.With the increase of the strain rate,it has almost no effect on the elastic modulus the way of the evolution of dislocation network,but contributes to the increases of the yield stress and tensile strength.Moreover,tension-compression asymmetry of Ni-based single crystal superalloys is also presented based on MD simulations.The tensile properties of this material is greater than its compressive properties.(3)Considering the impact on mechanical properties of alloy orientation,the three-dimensional models of the[110]?[111]orientation are established,and the different of the dislocation network structure and mechanical properties are compared.The results show that the[110]orientation dislocation network presents "?" structure in the XY plane,on the XZ,YZ is "?" structure;[111]orientation dislocation network is respectively triangle dislocation grids on the XY plane,quadrilateral grids on the XZ plane,and rectangular grid on the YZ plane.In the evolution of the dislocation network,three kinds of orientation dislocation structures tend to quadrilateral structure.In addition,the elastic modulus,yield strength and tensile strength of the alloy show obvious orientation dependence.