氚致B2相FeAl的氢脆及氦脆机制研究

Aluminides form of transition metals are well-known classes of structural intermetallics that possess several desirable properties such as oxidation and corrosion resistances, high melting points, relatively light weights and room-temperature ductilities. Alloys of iron-aluminides attract attention of researchers as promising materials in extreme technology because, they are promising candidates as substitute materials for steel. They are of well potential application in the fields of erospace, auto industry, energy exchanging system, filteration materials and so on. However, the poor ductility of intermetallics is the biggest obstacle for their large-scale practical application. Sensitivity to hydrogen causing so-called environmental embrittlement is commonly assumed to be one of the main reasons for the low plasticity and susceptibility to brittle fracture of iron aluminides in air at room temperature. Unfortunately, in addition to hydrogen embrittlement, the helium embrittlement has not been paid enough attention while the Fe-Al intermetallics using in the high temperature environments of tritium-containing atmosphere. In present proposal, we will focus the hydrogen embrittlement and helium embrittlement resulted from the application of Al2O3|Fe-Al|SS,(SS denotes the stain-less steel), which is considered as the ideal barrier of tritium permeation through the structural materials, to lower the tritium loss and the radiation risk in tritium processing plant. We adopt the ion implantation and thermal charging technologies to obtain the deauterium (tritium) and helium containing B2 phase FeAl single crystal. The micoroscopic behavior of hydrogen isotopes and helium in FeAl will be systematically investigated by the XRD, TEM, 3DAP, PAT, etc.Simutaneously, we will conduct the first-principles calculations and molecular dynamics simulations for the occuppation sites, diffusion, congesting and nucleation of hydrogen isotopes and helium in FeAl and the effects on the thermodynamical and mechanical properties of the FeAl bulk. The results figured out from this work should be useful to guide the design of the tritium permeation barrier materials, and also to complement the helium embrittlement behavior of the metal and alloy, specially for intermetallics, science.

铁铝金属间化合物具有良好的抗氧化和抗硫化腐蚀性能以及高温结构性质，而且轻质价廉，在航空航天、汽车工业、能量转换系统、过滤材料等领域具有广泛的应用前景。但高温涉氚环境使用导致Fe-Al的氢脆和氦脆是需要重点关注的科学问题。本项目拟采用离子注入和热充氘（氚）方法向B2-FeAl单晶中引入氘（氚）和氦，利用X射线衍射(XRD)、透射电镜(TEM)、三维原子探针(3DAP)、正电子湮灭(PAT)等技术从实验上系统研究FeAl中氢同位素及氦的微观行为；利用第一原理计算和分析动力学模拟，从电子和原子层次上深入理解氢同位素及氦在FeAl中的占位、扩散、聚集、形核以及由此诱发的氢脆和氦脆机制。通过项目研究，不仅对阻氚材料体系设计具有重要的指导意义，也对构建金属材料（尤其是金属间化合物）氢脆和氦脆的材料科学体系是必要的补充。

针对Fe-Al 金属间化合物由氢原子诱发室温脆性带来的潜在问题，项目采用实验研究结合理论模拟的方法，系统获得了FeAl 中氢同位素及氦的微观行为，深入理解FeAl的氢脆、氦脆机理。发现了氢、氦离子共注入造成FeAl晶格结构的无序化和非晶化，证实了双束注入带来的协同效应促进了气泡和空洞组织的形成。通过氘离子及氦离子的单独注入，发现晶界及缺陷组织均是氢同位素及氦的主要聚集和扩散通道，是产生氢脆和氦脆的主要场所。通过热充氚-贮存的方法制备含氚/氦-3的FeAl样品，获得了氚/氦的热解析脱附行为，证明了氚老化引发氦脆硬化，且该硬化效应随时间逐渐减弱。首次提出各向同性氢化Fe空位致FeAl氢脆形成源于氢原子与Al/Fe原子杂化作用与氢原子间库仑斥力竞争，为揭示氢脆现象背后隐藏的真正物理机制提供了证据，这一结果将通常的基于实验观测的FeAl氢脆主要出现在{100}面的现象向原子级方法前推了一步；提出通过He浓度控制或惰性气体掺杂方法抑制氢泡致氢脆的理论方法。公开发表文章11篇，中国工程物理研究科技创新自然科学类二等奖1项，授理发明专利2项，举办会议4次，参加国内外会议7次，培养4名研究生。研究结果将对氢同位素工业技术（特别是涉氚系统）及聚变堆发展中阻氚涂层材料设计具有重要指导意义，还可望深化金属间化合物材料氢脆物理机制的科学认识。