金属Nb级联碰撞的分子动力学模拟
收稿日期: 2019-06-20
修回日期: 2019-09-27
网络出版日期: 2019-11-06
基金资助
三峡大学人才专项经费项目(2016KJX03);水电机械设备设计与维护湖北省重点实验室开放基金项目(2019KJX08)
Molecular Dynamics Simulation of DisplacementCascades in Nb
Received date: 2019-06-20
Revised date: 2019-09-27
Online published: 2019-11-06
Supported by
Special Fund for Talents of China Three Gorges University(2016KJX03);Open Science Foundation of Hubei Key Laboratory of Hydroelectric Machinery Design & Maintenance(2019KJX08)
运用分子动力学方法研究了bcc结构Nb在辐照损伤初期因辐照诱发位移损伤形成和演化的微观过程以及原子机制。选取初级离位原子(primary knock-on atom，PKA)能量5~50 keV，模拟温度300 K，研究了Nb中级联碰撞产生的缺陷数量及其分布随模拟时间的演化，PKA能量对稳定Frenkel缺陷数目的影响，缺陷团簇的分布等。研究结果显示，级联碰撞会在体系中产生辐照缺陷，Frenkel 缺陷对数目和不同的PKA能量区间(5~30 keV和30~50 keV)之间满足不同的幂函数关系，所形成的缺陷大多数以点缺陷的形式存在，空位团簇成团率17%~35%，间隙原子团簇成团率23%~40%，PKA能量越高，空位越容易形成较大的团簇；级联碰撞产生的间隙原子形成了大量的沿<110>方向的哑铃型结构；当PKA能量高于30 keV时，级联碰撞将产生1/2<111>间隙型位错环和<100>空位型位错环。
马小强 , 杨坤杰 , 徐喻琼 , 杜晓超 , 周建军 , 肖仁政 . 金属Nb级联碰撞的分子动力学模拟[J]. 金属学报, 2020 , 56(2) : 249 -256 . DOI: 10.11900/0412.1961.2019.00203
Refractory metal Nb and its alloys are considered as promising materials in fusion reactor, where they are required to withstand a high neutron irradiation, because their excellent high temperature properties such as high temperature strength, good thermal conductivity and compatibility with most liquid metal coolants. The defects are created in atomic displacement cascade from the primary state of damage and subsequent evolution gives rise to important change in their microstructures and engineering properties. However, the evolution and aggregation of induced radiation defects in atomic level cannot be observed by experiment so far. In this work, molecular dynamics (MD) method is used to explore the microstructural formation and evolution of defects from the atomic displacement cascades in bcc-Nb. In the simulation, the energy range of primary knock-on atom (PKA) is chosen 5~50 keV and the simulation temperature 300 K. It is observed that the most of defects in bcc Nb are point defects at different PKA energies. The vacancy cluster rate varies from 17% to 35% and self-interstitial cluster rate varies from 23% to 40%. As the PKA energy increasing, vacancies usually tend to form larger clusters. The self-interstitial atoms form a dumbbell structure along the direction <110>. The 1/2<111> intermittent dislocation loop and <100> vacancy dislocation loop are produced when the PKA energy greater than 30 keV. The quantitative relationship between energy of PKA (EPKA) and number of survivals Frenkel pairs (NFP) is fitted by a power function with different parameters at low-energies (5~30 keV) and the high-energies (30~50 keV).
Key words： Nb; molecular dynamics (MD); displacement cascade; Frenkel pair; defect cluster
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