Mn在铁素体Fe-25%Cr合金中的迁移行为研究  

Study on Diffusion Behavior of Mn in Ferritic Fe-25%Cr Alloy

作　　者：马柯榕 张浩 张永帅 李坤[1] 杜秀娟 杨雯[2] MA Kerong;ZHANG Hao;ZHANG Yongshuai;LI Kun;DU Xiujuan;YANG Wen(School of Applied Science,Taiyuan University of Science and Technology,Taiyuan 030024,China;Shanxi Key Laboratory of Metal Forming Theory and Technology,School of Materials Science and Engineering,Taiyuan University of Science and Technology,Taiyuan 030024,China)

机构地区：[1]太原科技大学应用科学学院,太原030024 [2]太原科技大学材料科学与工程学院,金属材料成形理论与技术山西省重点实验室,太原030024

出　　处：《材料导报》2023年第19期153-157,共5页Materials Reports

基　　金：国家自然科学基金(51871158)。

摘　　要：铁素体合金是目前广泛应用于固体氧化物燃料电池(SOFCs)的连接体材料。掺杂Mn的Fe-Cr合金连接体会在服役过程中形成两层氧化膜,即Cr_(2)O_(3)和(Cr,Mn)_(3)O_(4),可有效避免其高温抗氧化性不足以及Cr挥发会毒化阴极等问题。而Mn原子在Fe-Cr合金体系中的迁移对(Cr,Mn)_(3)O_(4)的形成至关重要,但其微观机理尚不明晰。利用基于密度泛函理论的第一性原理方法,系统研究了Mn在铁素体Fe-Cr合金表面的迁移过程,以及由内部向表面的跃迁过程。分别构建并优化了Fe-25%Cr合金的晶体模型和合金(110)表面模型,计算了Mn在(110)表面的稳定吸附位和势能面分布,并确定了Mn在表面的迁移路径。进一步结合弹性带方法计算了各种迁移路径对应的迁移势垒。结果表明,Mn原子在表面迁移路径的势垒低于0.191 eV,以及由体内向表面跃迁路径的势垒低于4.480 eV。在此基础上计算了不同迁移路径的扩散系数随温度的变化关系,可知Mn更易沿表面迁移。从微观尺度上揭示了Mn原子在铁素体Fe-Cr合金内部向表面跃迁及在表面迁移的迁移机制,确定了Mn原子由晶体内部向表面的跃迁是影响Mn扩散的决定性因素,为铁素体Fe-Cr合金在SOFCs连接体上的应用提供了理论支持。Ferritic alloys are widely used interconnect materials for solid oxide fuel cells(SOFCs)at present.The Mn doped Fe-Cr alloy interconnects form two layers of Cr_(2)O_(3)and(Cr,Mn)_(3)O_(4)in the oxide film in service,which can effectively prevent the problems of insufficient high tempe-rature oxidation resistance and the volatilization of Cr.And the diffusion of Mn atoms in Fe-Cr alloy is crucial to the formation of(Cr,Mn)_(3)O_(4)layer,but its microscopic mechanism is still unclear.In this wrok,the possible diffusion pathways of Mn atoms on the surface and the hopping diffusion of Mn from the inside to the surface of the ferritic Fe-Cr alloy using first-principles based on density functional theory(DFT)were syste-matically investigated.The bulk model of perfect Fe-25%Cr alloy and the slab model of(110)surface are set up and optimized.The potential energy surface(PES)of Mn on the surface and the stable adsorption positions of Mn are calculated,while the possible pathways of Mn on the surface are found.Furthermore,we employ the nudged elastic band(NEB)method to calculate the energy barriers of different Mn diffusion pathways.The results present that the maximum energy barrier for the surface diffusion is about 0.191 eV,while it is 4.480 eV for the hopping diffusion.And the corresponding Mn diffusion coefficients versus temperature for different diffusion processes are obtained accordingly.Our results explain the microscopic mechanism of Mn hopping diffusion and the surface diffusion of ferritic Fe-Cr alloy from the atomic scale,and find that the hopping diffusion determines the Mn diffusion,which provides theoretical guidance of the ferritic Fe-Cr alloy for its future research and practical applications in SOFCs metallic interconnect.

关 键 词：铁素体合金 Mn迁移 扩散系数 第一性原理 

分 类 号：O469[理学—凝聚态物理]