Molecular Dynamics Simulation Study Of Multiple Interstitial Dislocation Loops

The evaluation of candidate structural materials for nuclear power plant reactors is one of the main challenges for structural materials in the next few decades.At present,the nuclear science and engineering community has been committed to studying the radiation resistance of nuclear materials.Iron-based alloy(austenitic steel or ferritic steel)is the main structural material in the reactor currently,and its service performance in the reactor exerts an important impact on the normal operation of the reactor.Therefore,It is an important issue to study the service performance of the iron-based alloy stack,especially its mechanical properties.After irradiating by high-energy particles in the reactor,many mechanical properties of the iron-based alloy will change significantly.The reason is that the point defects generated by irradiation will change the microstructure of the alloy through atomic migration,fusion,and other behaviors,which leads to the macroscopic mechanical properties degradation of the alloy.As a result,there is the excellent instructive significance for establishing a performance predictive model and selecting the best choice of structural material applied in the nuclear reactor through studying the evolution behavior of nano-scale point defects in iron-based alloys after irradiation.Computer molecular dynamics simulation provides an effective method to replace some experiments that cannot be performed in the laboratory.In this paper,molecular dynamics is applied to simulate the interaction among multiple interstitial dislocation loops.Within the framework of large-scale modeling methods,molecular dynamics(MD)atomic-scale research is very important because they enable people to understand the mechanism of interaction between atoms at the nanometer scale.Previous studies have found that in the irradiated iron-based alloys,the Burst vector is 1/2 [111] and [100] are the two main typical interstitial dislocation loops.Recent studies have shown that the growth of interstitial dislocation loops remains many mechanisms,the especially multi-body reaction is one of the important types.Understanding this mechanism will be essential to improve the radiation resistance of iron-based materials while the influence of radiation damage has always been the research frontier highlight in the nuclear materials field.In this paper,the computer molecular dynamics simulation method was applied to study the interaction between two interstitial dislocation loops that burgers vectors were both 1/2[111] in different temperatures,different sizes,and different positions,on the microscopic atomic scale.On this basis,the interaction among three 1/2[111] interstitial dislocation loops was also simulated,and the reaction mechanism was explored.However,in actual irradiated materials,besides the interaction between 1/2[111] dislocation loops,[100] dislocation loops and 1/2[111] dislocation loops also remain interaction.Therefore,this paper also discusses the interaction between one 1/2[111] and one [100] interstitial dislocation loops,and among two 1/2[111] and one [100] interstitial dislocation loops.The simulation results showed that the temperature and the relative position between the dislocation loops have an important influence on the reaction process.In terms of the size of the dislocation loops,[100] dislocation loops were always converted into1/2[111] dislocation loops.The interaction between interstitial dislocation loops is one of the mechanical properties that affect structural materials.The results of these simulations provide a possible explanation for understanding the evolution of structural material defects during irradiation.The interstitial dislocation loops produced in iron-based materials can induce radiation hardening and embrittlement,and affect the safety performance of the reactor.Different from the interaction among simple point defects or other simple type irradiation defects,In this study,molecular dynamics was applied to carry out an atomic-scale simulation study on the interaction among dislocation loops formed by irradiation damage,especially the interaction of multiple interstitial dislocation loops and the response of the corresponding mechanical properties evolution,which provides an important reference for the future research and development of radiation resistant materials.