Computing Research Of Temperature Effects And The Role Of Grain Boundaries In Radiation Damage Of Titanium

Failure behavior of radiation damage of nuclear structural materials is one of the key technical issues restricting the development of nuclear power, radiation-induced point defects over a long period of evolution and accumulation will severely affect the macroscopic properties of the material, eventually it will cause the failure of the material. Thermal peak "and" off-site peak play a very important role on the evolution and distribution of the radiation-induced defects in material. Studies have shown that a grain boundary in the material is a very important role for improving the anti-radiation performance of the material. However, many studies only qualitatively give the size and distribution of thermal peak "and" off-site peak area, and people did not give a consistent and firm conclusions of grain boundaries on the absorption mechanism of radiation-induced point defects, therefore, deep study of these issues is necessary for the understanding of the radiation damage behavior.In this paper, the adjusted molecular dynamics method in accordance with the characteristics of the cascade collision has been used to simulate the neutron irradiation damage behavior of hcp-Ti and the formation and evolution of irradiation-induced point defects under different conditions has been analyzed. The area size of thermal peak and off-site peak and the distribution of atoms are focused on, and the interaction of radiation-induced point defects and different structure of grain boundaries has been deeply studied according to the inherent defects in the grain boundary region.Research of the formation and evolution of single crystal system defect comes to the following rules:a) hcp-Ti shows a strong capacity of defect recovery in radiation damage; displacement threshold energy value exists obvious anisotropic characteristics; the results show that displacement threshold value is the smallest in the atoms close-packed direction, moreover, the displacement threshold value in different directions decreases as temperature increases. b) Under high temperature condition, more displacement atoms can move to a place far away from the initial position, and tend to form more stable Frenkel pairs. The defect evolution analysis also shows that the trend of stable defects number increases as temperature increases. c) Under steady state condition, the percentage of interstitials clusters is significantly higher than the vacancy’s under the same conditions of hcp-Ti system.Studies of temperature effect during irradiation have shown that the cascade collision stage basically ends at about0.4ps, and small cube model analysis method can be more accurate than the spherical shell model analysis method in analyzing the temperature distribution within the system, the size of the melting area and duration, results display that the size of melting area and duration increase as PKA energy and temperature increase; analysis results of atom radial distribution function indicate that the "melting area" appears obvious liquefaction phenomenon.Research system of grain boundary effect mainly consists of two parts:double-crystal system and polycrystal system. Results of double-crystal system show that grain boundary region of Σ38<0001>{7180} grain boundaries and Σ2<0001>{1120} grain boundary can be respectively described by dislocation model and vacancies, and the model of dislocation point defect sink and interaction characteristic of vacancy and point defect can perfectly explain the change features of both grain boundaries’vacancies and interstitials with the distance d of PKA atoms from the grain boundary in the irradiation stabilization phase; During irradiation, grain boundary consisted of vacancies has greater impediment on high-energy atoms than grain boundary consisted of dislocations, and impediment of grain boundaries on the high-energy atoms weakens as the temperature increases; The analysis results of polycrystal show that three grain junctions are the most susceptible to radiation damage and hcp-Ti nanocrystalline does not exhibit good anti-radiation performance during initial collisionIn this paper, a detailed simulation study of the defects、temperature effects and the role of grain boundaries of pure metal in the irradiation conditions has been made to prepare for the radiation damage research on alloys and phase boundary in the future, and it has a certain guiding significance for the design of the fast neutron reactors of next generation and structural materials of nuclear fusion reactor...