Molecular Dynamics Simulation Of Displacement Cascade Effects In Fe-Cr Alloy And Fe-Ni Alloy

For nuclear application in future fission and fusion reactors,Fe-based binary alloys: Fe–Cr and Fe–Ni alloys are promising candidate materials.The starting point for any neutron-irradiation-damage modeling effort is the study of the primary damage state produced by displacement cascades.Therefore,the displacement cascades of neutron irradiation with 6 different Cr concentrations(vary from2% to 20%)in Fe-Cr alloy and 6 different Ni concentrations(vary from 2% to 30%)in Fe-Ni alloy were simulated by molecular dynamics method.Special attention is paid to peak time,the maximum number of Frenkel pair(FP),the average number of surviving FPs,the fraction of vacancies and interstitial in clusters and the fraction of Cr or Ni atoms in interstitial position.Different Cr and Ni concentrations on the displacement cascade effects in Fe-Cr alloy and Fe-Ni alloy were analysised.The results show that the peak time,the maximum number of FP,the average number of surviving Frankel pairs and the average fraction of vacancies in clusters was approximately the same in random Fe-Cr alloys taking into account the associated standard errors(regardless of Cr concentration).And the average fraction of self-interstitial atoms(SIA)is a little bit bigger at higher Cr concentration than at lower Cr concentration.The number of Cr atoms associated with survived self-interstitial defects was investigated.The data shows that the concentration of Cr in interstitial positions is roughly two times as more as in the matrix.As for Fe-Ni alloy,according to the obtained results the peak time,the maximum number of FP and the average number of surviving Frankel pairs exhibit clear Ni concentration dependence,which reveals that increasing the Ni concentration in Fe-Ni alloy leads to fierce displacement cascade.Compared to the average fraction of SIAs in pure,the average fraction of SIAs varies from 10% to 50% as the Ni concentration increase while the average fraction of SIAs in pure Fe is around 40%.The average fraction of vacancies drops from 30% to 15% as the Ni concentration increase from 2% to 30%.As indicated in several Fe-Ni alloy cases,the concentration of Ni in interstitial positions is higher than in the matrix,which shows the gathering trend of Ni atoms in interstitial positions.