电子辐照条件下高纯铁中位错环演化的多尺度模拟

Multi-scale Modeling of Interstitial Dislocation Loop by Electron-irradiation High Purity Iron

辐照诱导材料微观结构演化导致的材料力学性能降级或尺寸不稳定性是限制反应堆安全与经济性的关键因素之一。本文基于速率理论建立了辐照诱导材料微观结构演化的物理模型,并开发了模拟程序Radieff。采用分子动力学计算了高纯铁中缺陷的形成能、结合能、迁移能以及间隙原子位错环的构型,在此基础上模拟了电子辐照诱导高纯铁内位错环的演化过程,并与实验结果进行了对比。基于分子动力学的计算结果表明,当间隙原子团簇包含3个间隙原子时,团簇的排列方式为〈110〉构型,间隙原子团簇包含4个以上间隙原子时,团簇排列方式变为〈111〉构型。此外基于Radieff研究了400~600K温度范围内,损伤速率为1.5×10-4 dpa/s电子辐照条件下,位错密度对位错环演化的影响,位错密度对位错环数密度及其平均尺寸的影响取决于位错以及间隙原子团簇对间隙原子的阱强度;在464K和550K温度下辐照,位错环数密度及其平均尺寸分别在位错密度增加到1011 cm-2和1010 cm-2后急剧减小,这是由于此时位错对间隙原子的阱强度会大于间隙原子团簇对间隙原子的阱强度。

The microstructure evolution induced by irradiation on materials will lead to dimensional instability and mechanical property degradation of structure materials,which is one of the major factors to limit the safety and economical feature of nuclear plants.In this work,aphysical model and numerical code named Radieff were developed based on rate theory,and the subsequently molecular dynamics（MD）method was used to calculate the input parameters of the model,such as formation energy,binding energy,migration energy and the stable configuration of interstitial loops.Finally,the interstitial loop evolutions in high purity iron by 1MeV electron irradiation were reproduced with the model and code,and calibrated by experiment results.According to the MD results,it is found that the stable configuration is 〈110〉direction for 3self-interstitial atoms（SIAs）cluster,then turn to 〈111〉direction for larger cluster.The effects of dislocation density on the evolution of interstitial loops induced by electron irradiation were studied by Radieff under the temperature of 400-600 Kand the dose rate of 1.5×10-4 dpa/s.The effect of dislocation density on number density and size of interstitial loops depends on the comparison of the sink strengths between dislocation and interstitial clusters to SIAs.Under the radiation temperatures of 464 Kand 550K,the number density and size of interstitial loops decrease rapidly when the dislocation density gets to 1011 cm^（-2）and 1010 cm^（-2） respectively,as a result of lager sink strengths of dislocation than interstitial clusters to SIAs.