FeCuMnNi合金体系中溶质-空位团簇的原子尺度研究

Atomistic Study of Solute-vacancy Cluster in FeCuMnNi Alloy System

反应堆压力容器(reactor pressure vessel,RPV)是核反应堆中不可更换的关键部件,辐照脆化是影响其安全运行的主要因素。溶质缺陷团簇是中子辐照后RPV钢中的主要微观缺陷,研究其形核长大机制有助于理解RPV钢的辐照损伤行为。本文采用Metropolis蒙特卡罗方法模拟得到FeCuMnNi合金体系中溶质-空位团簇的稳定构型,结合分子静力学方法从原子尺度研究溶质原子与空位团簇的作用机理,分析探讨溶质-空位团簇的形核长大机制。结果表明,在FeCuMnNi合金体系中,Cu原子相较于Mn、Ni会优先在空位团簇表面偏析,形成的溶质-空位团簇为球形壳层结构;Mn会促进溶质-空位团簇的长大,而Ni对于溶质-空位团簇尺寸的影响很小,Mn、Ni存在协同效应,会促进溶质-空位团簇的形核长大;溶质-空位团簇中溶质原子的结构和能量存在相关关系,空位团簇可直接改变其附近溶质原子的结构,导致内层溶质原子能量显著高于外层原子,长大过程逐渐由空位团簇主导转变为外层溶质原子主导。以上结果有助于理解中子辐照后RPV钢中微观缺陷的形成和演化行为,推动RPV钢辐照脆化行为的模拟预测。

Reactor pressure vessel(RPV)is an irreplaceable component in pressurized water reactors.It carries internal components,fuel assemblies and primary cooling water.Its integrity plays an important role in the safe operation of the reactor.Microscopic defects caused by neutron irradiation can cause radiation hardening and radiation embrittlement of RPV steel,increasing the risk of brittle fracture of RPV steel.Accurately characterizing the microscopic defects is of great significance for predicting the macroscopic properties of RPV steel.Solute defect clusters are the dominant radiation defects in RPV steel.Because they are rich in solute atoms Cu,Mn,Ni,etc.,they can also be called Cu-rich precipitates and Mn-Ni-rich precipitates.At present,there are few studies on the nucleation and growth of precipitates dominated by vacancy clusters.Due to the limitations of microscopic characterization technology,it is difficult to directly observe solute-vacancy clusters in RPV steel.In this work,the solute-vacancy clusters generated in RPV steel after irradiation were focused.Taking the FeCuMnNi alloy system as the research object,the nucleation and growth process of solute-vacancy clusters were explored.The Metropolis Monte Carlo method was used to simulate the stable configurations of the solute-vacancy clusters in different RPV model alloys.The molecular statics method was used to study the interaction mechanism between solute atoms and vacancy clusters.The results show that in FeCuMnNi alloy system,Cu atoms preferentially segregate on the surface of vacancy clusters than Mn and Ni atoms,and the solute-vacancy clusters have a spherical shell structure.Mn can promote the growth of solute-vacancy clusters,while Ni has little effect on the growth of solute-vacancy clusters.Mn and Ni elements have a synergistic effect,which can promote the growth of solute-vacancy clusters.There is a correlation between the structure and energy of solute atoms in solute-vacancy clusters.Vacancy clusters can directly change the structures of solute atoms nearby,causing the inner solute atoms have significantly higher energy than the outer atoms.The growth process of solute-vacancy clusters can change from being dominated by vacancy clusters to outer solute atoms.The results are helpful to understand the formation and evolution behaviors of microscopic defects in RPV steel under neutron irradiation,and promote the prediction of irradiation embrittlement.In the future,to fully reveal the nucleation and growth process of solute-vacancy clusters,we will carry out research from a kinetic perspective using the kinetic Monte Carlo method or the cluster dynamics method.