The Construction And Application Of Potential For Nickel-Chromium System

In the 21th century,the problem we have to solve urgently is the shortage of energy.Compared with the traditional fossil energy,nuclear energy,fission energy especially,has become the key in the future's energy development due to its plenty stock and high energy density.Among the six candidate systems for the fourth generation?Gen-IV?fission reactor,the Thorium-based molten salt reactor nuclear energy system can utilize fission energy effectively for its high thermal efficiency,high electric power,high safety and low operating pressure.It has also become one of the special items in strategic technology initiated by the Chinese Academy of Sciences.Being the structure of MSR's power system,the macroperfomance will be affected due to the Frenkel defects,holes resulting from the high energy irradiation.The deterioration of performance such as swelling,embrittlement,and decrease of ductility will appearance,resulting in nuclear leakage and nuclear proliferation.Hastelloy,which has great prospects in the design of molten salt reactor due to its good corrosion resistance and high temperature resistance,has become one of the candidates for the structure of molten salt reactor.Therefore,it is very necessary to delve into the anti-irradiation properties of Hastelloy.Actually,the experimental study of anti-neutron irradiation for Hastelloy is costly and technically difficult.Molecular dynamics simulation is an effective way to solve these problems.Based on the theory of MAEAM,the interatomic interaction potential of the Ni-Cr system?main component of Hastelloy?is constructed,the simulation of irradiation cascade is studied and the impact of temperature,primary knock-on atom energy,composition on the result of irradiation are also discussed.In this work,the element potential of Ni and Cr are constructed with the MAEAM theory that developed by our group.The physical properties tested are in good agreement with the experimental values and the first-principles results.Compared with the existing Ni potential,our potential improves the shortcomings of elastic constants in Mishin's,Farkas's and Voter's potentials.It also solves the problem in Lee's,Voter's and Bonny's potentials that the order of formation energy in<110>,<111>direction is wrong.The problem that the unstable stacking fault energy of Lee's,Voter's potential is significantly higher and Bonny's,Mishin's are obviously lower has also been solved.As for the published Cr potential,the cohesive energy of Olsson's potential is lower than the experimental value,the self-interstitial atom's configuration in<111>direction and octahedral are unstable in Lee's potential,the Cauchy pressure relationship under different temperatures in Olsson's,Lin's,Lee's potential can't be reflected correctly and the structure of dislocation core doesn't match the result of the first principle,these shortcomings have been improved furtherly.With the obtained elemental potential,we constructed the Ni-Cr potential furtherly by fitting the formation energy,Ni₂Cr's elastic constant and the binding,migration energy of different point-defect solute configurations in Ni-based.In order to evaluate the anti-irradiation performance of Hastelloy and optimize the composition comprehensively,the cascade irradiation of Ni-Cr system is simulated preliminarily with the constructed potential.The effects that temperature,primary knock-on atom energy and Cr composition have on the irradiation results are discussed.The study found that the temperature has little effect on the number of stable defects,while the primary knock-on atom energy has a greater influence and the higher energy,the more number of stable defects.The temperature will have a significant effect on the number of stable defects when primary knock-on atom energy is 50 keV.For the system with the same primary knock-on atom energy at 100K or300K,the number of defects always increases with the increase of Cr concentration.When the primary knock-on atom energy is larger than 30 keV,there still exist large defect clusters under stable state.We have also found that the interstitial atoms formed by Cr atoms are very few in the case of low energy,the number of Cr interstitial atoms has increased significantly at the energy of 50 keV.