合金元素Sn,Nb对锆合金腐蚀氧化膜相稳定性影响的第一性原理研究  

First-principles study on effects of alloying elements Sn andNb on phase stability of corrosion oxide films ofzirconium alloys

作　　者：陈暾 崔节超 李敏[1] 陈文[1] 孙志鹏 付宝勤 侯氢[1] Chen Tun;Cui Jie-Chao;Li Min;Chen Wen;Sun Zhi-Peng;Fu Bao-Qin;Hou Qing(Key Laboratory for Radiation Physics and Technology,Ministry of Education,Institute of Nuclear Science and Technology,Sichuan University,Chengdu 610064,China;Science and Technology on Reactor System Design Technology Laboratory,Nuclear Power Institute of China,Chengdu 610200,China)

机构地区：[1]四川大学原子核科学技术研究所,辐射物理及技术教育部重点实验室,成都610064 [2]中国核动力研究设计院,核反应堆系统设计技术重点实验室,成都610200

出　　处：《物理学报》2024年第15期162-171,共10页Acta Physica Sinica

基　　金：四川省自然科学基金(批准号:2023NSFSC0044);中央高校基本科研业务费专项资金资助的课题

摘　　要：锆合金的水侧腐蚀是核燃料棒包壳材料设计的关键问题之一.包壳材料的耐腐蚀性能与锆合金氧化膜中t-ZrO_(2)含量和t-m相变密切相关.目前,Zr-Sn-Nb系合金是新型锆合金发展的主流方向.合金元素Sn,Nb在氧化膜中可呈现多种价态,显著影响ZrO_(2)稳定性,然而Sn,Nb对t-ZrO_(2)含量和t-m相变的影响机制尚不明晰.本文基于第一性原理计算了不同价态Sn,Nb掺杂ZrO_(2)的晶体结构性质、形成焓和氧空位形成能,从原子尺度揭示了Sn,Nb对ZrO_(2)稳定性的影响机理.研究表明Sn^(2+),Nb^(3+)引起显著晶格膨胀;Sn^(4+)则造成轻微晶格膨胀,而Nb^(5+)引起晶格收缩,可见高氧化态下Nb比Sn更利于减小氧化膜的内应力.低价合金元素降低ZrO_(2)稳定性,且会增大t,m相形成能差距;高价的Nb^(5+),Sn^(4+)均可提高t-ZrO_(2)相对稳定性从而抑制t-m相变,其中Nb^(5+)效果显著,Sn^(4+)则作用微弱.0—3.5 GPa范围内,t-ZrO_(2)相对稳定性随压力增大而增强.合金元素的低价态比高价态更利于在t-ZrO_(2)中形成氧空位,因而在氧化膜/金属界面附近低氧化态区域,低价元素和压应力是稳定t-ZrO_(2)的主要因素.通过电子结构分析,发现氧空位形成能与合金元素离子和氧空位间的电荷转移幅度(或电子局域化程度)呈正相关.这些结果有助于针对锆合金耐腐蚀性的成分优化和结构设计.Water-side oxidative corrosion of zirconium alloy is a key problem in the design of nuclear fuel rods cladding materials in pressurised water reactors(PWRs),and its corrosion resistance is one of the main factors limiting service life.At present,Zr-Sn-Nb system alloys are still the main development direction of advanced zirconium alloys.Sn and Nb can exhibit a variety of valence states in the oxide film of the cladding and significantly affect the stability of ZrO_(2).However,the influence mechanism of Sn and Nb on the fraction of t-ZrO_(2)and the t-m phase transition is unclear.In this work,the lattice properties,formation enthalpies,and oxygen vacancy formation energy of ZrO_(2)under the doping conditions of Sn and Nb with different valence states are calculated based on the first-principles,and the influence mechanism of Sn and Nb on the stability of ZrO_(2)is revealed at an atomic scale.The results show that there is a significant difference between the effects of Sn and Nb,as well as between low-valent and high-valent elements.Sn^(2+)and Nb^(3+)cause lattice swelling to be significantly distorted,Nb^(5+) causes lattice to shrink,which contributes to reducing the stresses within the film,and Sn^(4+)leads the lattice to slightly swell.The low-valent elements all make ZrO_(2)less stable and are unfavourable for the stability of t-ZrO_(2)relative to m-ZrO_(2).The high-valentNb^(5+)and Sn^(4+)promote the relative stability of t-ZrO_(2),thus inhibiting the t-m phase transition,withNb^(5+)having a significant effect and Sn^(4+)having a weak effect.The relative stability of t-ZrO_(2)increases with pressure rising in a range of 0–3.5 GPa.Compared with high-valent elements,the low-valent elements are favourable for introduing oxygen vacancies into t-ZrO_(2),thus stabilising the interfacial t-ZrO_(2)and enhancing the corrosion resistance of the cladding.By investigating the electronic structure,it is found that the oxygen vacancy formation energy is positively correlated with the magnitude of charge transfer(or degre

关 键 词：第一性原理 Zr-Sn-Nb 合金 氧化膜 相稳定性 

分 类 号：TL34[核科学技术—核技术及应用] O469[理学—凝聚态物理]