摘要
奥氏体不锈钢或镍基合金等FCC构型的核反应堆堆芯结构件材料中易于观测到晶间孔隙或晶内各向异性孔隙.孔隙内填充有少量气体,其形貌与晶体表面各向异性有关,又易于在晶界形核受晶界特性调控.本文通过建立耦合晶面各向异性与孔隙-晶界交互作用的自由能泛函模拟孔隙及其形貌演化,研究结果表明,He气体诱导孔隙形核,He气体浓度越高,孔隙的孕育期越短,形核越快,长大速率越大.晶界为孔隙形核提供非均质位点,孔隙优先在晶界处形核长大,形成沿晶析出的高密度弥散孔隙.晶内孔隙呈各向异性特征,受界面能各向异性模数、强度及晶体取向调控;晶间高密度孔隙相互作用且受晶界影响,各向异性形貌不显著,位于晶界中间的孔隙近似呈现椭圆形.本文的结果与实验结果符合得较好,启发堆芯服役构件的寿命预测和堆芯材料设计.
Intergranular or intragranular anisotropic pores can be easily observed in the FCC structure of nuclear reactor core structural materials,such as austenitic stainless steel or nickel-based alloys.Austenitic stainless steel contains a certain amount of nickel(Ni),and Ni undergoes transmutation reaction under neutron irradiation to produce helium.Helium combines with vacancy and continuously absorbs more helium and vacancy,evolving into under pressure pores filled with a small amount of helium.The morphology of pores is influenced by both the surface anisotropy of the crystal and grain boundary characteristic because pore nucleation predominantly occurs at grain boundary.The swelling effect caused by pores and the embrittlement effect of high temperature helium are related to the morphology,size and distribution of pores.The phase field method can couple multiple physical fields and accurately describe the effects of material microscopic defects on pores.In this study,we use the phase field method to simulate the evolution and morphology of pores,establishing a free energy functional coupling between crystal plane anisotropy and pore-grain boundary interactions.Our results demonstrate that helium gas induces pore nucleation,with higher concentrations leading to shorter incubation period,faster nucleation rate,and greater growth rate.Grain boundaries act as heterogeneous nucleation sites for helium pores,leading to the formation of pores along these boundaries and high-density diffusion pores within the grains.The intragranular pores exhibit anisotropic characteristics regulated by interfacial energy’s anisotropic modulus,the strength of the anisotropy,and crystal orientation.The high-density intergranular pores interact with each other significantly and are influenced by grain boundaries,while the anisotropic morphology is negligible.Additionally,it has been observed that the pores located in the middle of grain boundaries tend to become an elliptical.The stress inside the pores that contain a small amount of helium gas is negative,which is lower than the value in the matrix.These findings presented herein align well with experimental results,which inspires the prediction of service life of core components and the design of core materials.
作者
程大钊
刘彩艳
张超然
屈佳辉
张静
Cheng Da-Zhao;Liu Cai-Yan;Zhang Chao-Ran;Qu Jia-Hui;Zhang Jing(State Key Laboratory of Solidification Processing,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China;School of Materials Science and Engineering,Xi’an University of Technology,Xi’an 710048,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第22期163-173,共11页
Acta Physica Sinica
基金
国家自然科学基金(批准号:U2267253,51704243)
陕西省自然科学基础研究计划(批准号:2022JM-238)资助的课题.
关键词
孔隙
各向异性
相场
辐照
pores
anisotropic
phase field
irradiation
