Fe-C合金中辐照缺陷特征的剂量率效应计算模拟

目的尝试采用计算模拟方法探究剂量率对辐照微结构特征的影响,探究常温辐照下剂量率效应的机理。方法采用动力学蒙特卡罗(OKMC)方法,结合近些年第一性原理和分子动力学的计算参数,研究了常温下铁-碳体系中辐照缺陷随剂量率的变化特征。结果在较低的剂量范围(<0.01 dpa)内,间隙型位错环的密度随剂量率的增加而增加;但在较高的剂量范围内,高剂量率辐照呈现较低的间隙型位错环密度、较大的缺陷尺寸。通过比较不同剂量率下的位错线对点缺陷的吸收数目,把剂量率在不同剂量范围内的特征归结于位错吸收与缺陷复合之间的竞争。结论在较低的剂量范围内,位错吸收具有重要影响,随着剂量率的增加,位错吸收的缺陷数目显著减少;而在较高的剂量范围内,基体中间隙-空位缺陷的复合随剂量率的增加而显著增加,以至于高剂量率辐照可能产生较低的辐照硬化。文中的工作对理解剂量率效应的机理提供了一定的科学依据,为离子束模拟中子辐照提供了一定的科学参考。

Dose-Rate Effect Simulation of Radiation Defect Characteristics in Fe-C Alloys

This paper attempts to explore the influence of dose rate on the microstructure characteristics of irradiation using computational simulation and to explore the mechanism of dose rate effect under normal temperature irradiation. Object Kinetic Monte Carlo (OKMC) method is used to study the variation characteristics of radiation defects with dose rate in the Fe-C system at room temperature. Simulation results show that the density of interstitial loops increased with the increasing dose rate at the lower dose range (<0.01 dpa), but high dose rate irradiation showed a lower interstitial-loops density, a larger average loop size at a higher dose range. By comparing the number of dislocation absorpted defects at different dose rates, it is concluded that the characteristics of dose rate in different dose ranges are attributed to the competition between dislocation absorption and defect recombination. Dislocation absorption play an important role in the low dose range. With the increase of dose rate, the number of defects absorbed in dislocation lines decreased significantly. However, at higher dose ranges, the recombination of interstitial-vacancy defects in the matrix probably increases significantly at the higher dose rate, so that high dose rate irradiation result in lower interstitial loop density and irradiation hardening. The work in this paper provides a scientific basis for understanding the mechanism of the dose rate effect and a scientific reference for ion beam simulation of neutron irradiation.