摘要
锆合金因具有强的耐腐蚀能力、低的热中子吸收截面等特点而被广泛应用于核反应堆中。经过六十多年的发展,锆合金已由第一代锆-1合金发展至第二代锆-2、锆-4合金以及第三代的N36、ZIRLO、M05等。氢化物析出是造成核级锆合金力学性能变差的主要原因,氢主要来自于金属锆和水发生的腐蚀反应,它通过扩散运动进入金属基体,并滞留在基体中。锆合金中氢化物的种类及性质一直以来备受研究者们的关注。目前发现的氢化物有四种,但由于ζ-ZrH 0.5(bct)、γ-ZrH(fct)两种氢化物为亚稳态,且ζ相氢化物存在时间极短,现阶段的实验设备或实验方法无法在如此短的时间尺度上对其进行观察,因此大量关于氢化物的研究均集中于δ-ZrH 1.4—1.7(fcc)、ε-ZrH 2(fct)这两种稳定相上。锆合金包壳或结构件的工作环境均为高温,高温下基体中的滞留氢将发生脱附。在停堆及其他条件下吸收的氢超过极限固溶度后将以氢化物的形式析出,造成晶格畸变,而在高温时氢脱附使晶格畸变消失。此循环过程中,材料内部将逐渐累积大量微缺陷,加速材料老化。大量研究者均采用纯ZrH 2粉末样品研究氢的脱附行为,但实际服役的锆合金中还含有大量合金元素,合金元素的存在会影响氢的滞留状态以及脱附行为。因此以纯ZrH 2粉末样品中氢脱附温度的实验数据作为依据来判断锆合金的适用条件并不严谨,需研究不同种类锆合金中不同氢化物的脱附温度。热脱附谱(TDS)技术是研究金属及合金中滞留氢及其同位素的有效方式之一,但采用TDS设备测定锆合金中氢的脱附行为存在一定的局限性。此外,锆合金表面普遍存在一层氧化层,其会影响氢的脱附行为,在脱附过程中当氢扩散至氧化层时,氧化层中的氧将捕获部分氢原子形成氢氧键,使脱附量减少,同时滞后氢的脱附,使脱附温度升高。因此,实验数据上的脱附温度升高并不意味着基体内的氢化物实际脱附温度升高,只是氢向外扩散的过程受到了氧化层的阻挡,使脱附谱向高温方向移动。本文总结了氢化锆脱附行为的研究进展,分别对氢化物的结构、氢的来源、氢滞留量、TDS设备局限性以及氢化物脱附行为进行了介绍,指出了当前研究的不足之处,并展望了未来研究的方向。
Zirconium alloys have been widely used in nuclear reactors due to their strong corrosion resistance and low thermal neutron absorption interface.After more than 60 years’development,zirconium alloys have evolved from the first generation of zirconium-1 alloys to the second generation of zirconium-2,zirconium-4 alloys and the third generation of N36,ZIRLO,M05 alloys.Hydrogen precipitation will reduce the mecha-nical properties of zirconium alloys.Hydrogen mainly comes from the corrosion reaction between zirconium and water,which enters the metal matrix through diffusion and retains in the matrix.The types and properties of hydrides in zirconium alloys have attracted much attention.So far,there are four types of hydrides,but two of them(ζ-ZrH 0.5(bct)andγ-ZrH(fct))are metastable.Moreover,the presence ofζphase hydride is extremely short,the current experimental equipment or experimental methods cannot be observed at such a short time scale.Hence,many experimental studies on hydrides are concentrated inδ-ZrH 1.4-1.7(fcc)andε-ZrH 2(fct).The working environment of the zirconium alloys is high temperature,while the retained hydrogen in the matrix will desorb at high temperature and lead to the distortion caused by precipitate phase disappear.During this cycle,many micro defects gradually accumulate inside the material,then accelerate the materials aging.It was found that many researchers used pure ZrH 2 powder to study the desorption behavior of hydrogen in zirconium,but the actual serviced zirconium alloys contain other alloying elements,their existence will affect the retention state and desorption behaviors of hydrogen.Thermal desorption spectroscopy(TDS)is one of the effective ways to investigate the retention state of hydrogen and its isotopes in metals and alloys,however,TDS has certain limitations in determining the desorption behavior of hydrogen in zirconium alloy.Besides,the surface of zirconium alloys commonly covered by an oxide layer.When hydrogen diffuses into the oxide layer,the oxygen atoms in the oxide layer will trap some hydrogen atoms by forming hydrogen-oxygen bond.This bond reduces the amount of desorption,delays the desorption,and rises the desorption temperature.Therefore,the increase in desorption temperature on the experimental data does not mean that the actual desorption temperature of the hydride in the matrix,but the process of hydrogen diffusion is blocked by the oxide layer.This review summarizes the research progress of the desorption behavior of zirconium hydride,introduces the structure of hydrides,the source of hydrogen,the hydrogen retention state,the limitations of TDS and the desorption behavior of hydrides respectively,points out the shortco-mings of the research in desorption behavior of zirconium hydrides and prospects the future research directions.
作者
杨振飞
史鹏
敖冰云
YANG Zhenfei;SHI Peng;AO Bingyun(Institute of Materials,China Academy of Engineering Physics,Jiangyou 621700,China;Science and Technology on Surface Physics and Chemistry Laboratory,China Academy of Engineering Physics,Jiangyou 621908,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2020年第5期102-108,共7页
Materials Reports
基金
国家自然科学基金(21771167)~~
关键词
反应堆包壳
锆合金
氢化物
热脱附谱技术
二氧化锆
reactor cladding
zirconium alloy
hydrides
thermal desorption spectroscopy(TDS)method
zirconium dioxide
作者简介
杨振飞,2016年毕业于四川大学金属材料工程专业,获工学学士学位。现为中国工程物理研究院材料研究所硕士研究生,在敖冰云研究员指导下进行研究。主要研究领域为合金元素对锆合金中氢脱附行为的影响;敖冰云,男,1976年1月3日生,博士,研究员。主要从事核材料的实验和理论研究,负责科学挑战计划、国家自然科学基金、国防系统预先研究专题等在内的多项科研项目。公开发表核材料领域的学术论文50余篇,多次应邀参加核材料领域的国内外学术会议,并做大会特邀报告或邀请报告。因在核材料老化实验和理论研究上取得的创新成果而获得第十三届邓稼先青年科技奖,shipeng@caep.cn,aobingyun@caep.cn。
