Simulation Study On The Interactions Between Screw Dislocation And Irradiation Defects In Austenitic Stainless Steel

Nuclear energy,with its advantages of efficient low carbon,is globally used to increase electrical power,optimize energy structure,and cope with climate change.In order to ensure the safe operation of the reactor,austenitic stainless steel with good comprehensive performance is often widely used as a structural material in the nuclear industry.Due to the long-term irradiation of high-energy particles,various types of defects are induced.And these irradiation-induced defects are an important reason for the irradiation damage of austenitic stainless steel.Irradiation damage fundamentally induces the changes of material properties,which will directly affect the safety and life of the nuclear reactor.From the perspective of dislocation theory,changes in various mechanical properties induced by irradiation can be regarded as caused by irradiation hardening.Irradiation hardening is the fact that irradiation defects hinder the dislocations during the movement and multiply dislocations.Irradiation-induced point defects and the evolution of defect clusters will strengthen the dislocation launch and movement hindrance.In a word,the interaction of these defects with dislocations is the crucial reason for irradiation hardening.Therefore,it is profound to study the interaction between the defects induced by irradiation and dislocations from the microscopic level and analyze the contribution of various types of defects to the irradiation hardening in materials.In this paper,using molecular dynamics simulation,we first simulated the interactions of screw dislocation(SD)and stacking fault tetrahedron(SFT)in Fe-10Ni20Cr(a model alloy of austenitic stainless steel)and pure Ni system under high temperature and high shear rate conditions.Four interaction processes were primarily found,including(1)partial absorption,(2)sheared with ledges,(3)bypassing,and(4)restored through double cross-slip.In Fe-10Ni-20Cr alloy,the results of the interactions are affected by the intersection position of SD and SFT,but they are basically not related to the SFT size.In addition,the occurrence of cross-slip affects the interactions,and there exist greater critical resolved shear stress(CRSS)value in the interactions of cross-slipping.Studies have shown that the occurrence of cross-slip is related to the stacking fault energy(SFE)and the distribution of alloy solute atoms.Comparing with the results of Ni,we speculate that the SFE is an important factor affecting the interactions between SD and SFTs,and thus irradiation hardening induced by the SFT-dislocation interaction.Secondly,under low shear rate conditions,we study the interactions of SD with SFT,Frank loop,and void.The SD and SFT are mainly based on the results of first and second categories.After interactions,the main morphologies of Frank loop are as follows:(1)new stacking faults are form;(2)intrinsic stacking faults are eliminated and it transforms into a 1/2<011>loop;(3)it is completely absorbed into a sessile helical turn.After the interactions,voids almost have no change,only with slight shear deformation.Studies show that the higher the temperature,the greater the impediment of the same size defects to the movement of screw dislocations.Conversely,the smaller.Through statistical analysis of CRSS during the interactions of SD and three defects,it is found that the Frank loop has the most hindrance to the movement of SD,the second is void at low temperatures,and the last is SFT.The simulation work in this paper can provide a data reference for irradiation hardening induced by the interaction of dislocations and defects in austenitic stainless steel,and they can also be used to predict the change trend of austenitic stainless steels with macroscopic performance in a certain extent.