Molecular Dynamics Simulation Of The Effect Of Grain Boundary Orientations On Tensile Mechanical Properties Of AI_0.1CoCrFeN High Entropy Alloy

In recent years,high entropy alloys have been widely studied by experts and scholars in the field of materials science and engineering due to the excellent strength,hardness and good wear resistance.The mechanical properties of high entropy alloys largely determined by the properties of grain boundaries and the distribution of special grain boundaries.Therefore,the influence of grain boundaries on tensile mechanics has attracted the attention of scholars in this field.It is particularly important to study the mechanism of the influence of grain boundaries with different orientations on the mechanical properties of high entropy alloys.With molecular dynamics simulation method,coincidence site lattice is adopted in this paper to establish different orientation grain boundaries for the face-centered cubic crystal structure Al0.1CoCrFeNi model of high entropy alloys.Al0.1 CoCrFeNi high entropy alloys containing different grain boundary(?3,?9,?27)are uniaxial tensiled under different strain rate and temperature.The impact mechanism of tensile mechanical properties are analyzed under different conditions on the different orientation of grain boundary.The simulation results show that the Young's modulus and density of Al0.1CoCrFeNi high entropy alloy are consistent with the existing physical experimental results,which verifies the accuracy of the established model and the potential function used.Compared with no grain boundary system,Young's modulus and yield strength of Al0.1 CoCrFeNi high entropy alloy containing grain boundary ?3 are higher.Compare stress-strain curves of Al0.1CoCrFeNi high entropy alloy with three different grain boundaries system of the ?3,?9,?27 with different strain rate and temperature order axis stretching process,stress-strain curve of the three kinds of grain boundaries have undergone a similar change process.When the strain is small,it is a process of elastic deformation.The stress further increases and finally reaches the peak stress,and then begins to yield.Compare Young's modulus and yield strength under different conditions:the Young's modulus and yield strength of the ?3 grain boundary are the largest.In the tensile process of grain boundary Al0.1CoCrFeNi high entropy alloy with different orientations at different strain rates,it is found that the yield strength of the system increases with the increase of strain rate.However,the value of Young's modulus does not change much.The microstructure diagram shows that the increase of strain rate will increase the number of stacking faults and dislocations,and form the entanglement of dislocations near the grain boundary,which may result in the stress concentration at the grain boundary.The mechanical properties of high entropy alloy may be improved.The results show that the Young's modulus and yield strength of Al0.1CoCrFeNi high entropy alloys of different orientations grain boundaries decrease with the increase of temperature.By observing the microscopic diagram,it is found that with the increase of temperature,the dislocation movement increases and the extinction of the dislocation occurs,which result in the decrease of the dislocation density and the decrease of the mechanical properties.C ompare different grain boundary ?3 and ?9 in microscopic diagram,main dislocation is 1/6<112>Shockley inperfect dislocation.For grain boundary ?27,main dislocation type is 1/6<110>Stari-rod inperfect dislocation.