B对Mo等元素在奥氏体钢/Cr2O3界面占位倾向影响的理论研究

超级奥氏体不锈钢中因含有更高铬、钼含量,具有极高的耐点蚀、晶间腐蚀性能,这与Mo等合金元素对钝化膜结构的影响密切相关,尤其含硼超奥钢钝化层表面Cr、Mo含量明显增加,但其原子层次的微观作用机制尚不清楚.本文采用第一性原理方法,研究了置换原子(Mo、Mn、Ni、Si),及间隙原子B在fcc-Fe/Cr₂O₃界面占位倾向,并分析了可稳定存在于界面B对这些元素偏析倾向的影响.结果表明:Mo、Mn、Ni、Si、B均可与fcc-Fe/Cr₂O₃界面结构体系形成稳定结构;Mo、Ni倾向分布于界面基体侧,Mo有向氧化层扩散的趋势,B处于fcc-Fe/Cr₂O₃界面基体侧更稳定,Mn、Si易分布于氧化层中;存在于界面B对四种元素在fcc-Fe/Cr₂O₃界面体系中的占位影响不同,有利于Mn、Mo偏析于界面基体侧,但抑制Mo向界面基体侧的偏析程度,使得Si、Ni更均匀的分布于基体. Mo等合金元素分布于界面时的态密度来看,界面处M...

Theoretical Study on Segregation Behavior of Mo and metals at the fcc-Fe/Cr2O3 interface without or with B

Super austenitic stainless steel has extremely high resistance to pitting and intergranular corrosion. This is because the high content of chromium and molybdenum has an important impact on the structure of the passivation film, but the mechanism of chromium and molybdenum on the passivation layer is not yet clear. Therefore, this paper adopts the first-principles method to conduct theoretical explorations of the material system, studies the segregation tendency of replacement atoms (Mo, Mn, Ni, Si) and interstitial atoms B at the fcc-Fe/Cr2O3 interface, and analyzes the influence of B on the propensity of these elements. The calculation results show that Mo, Mn, Ni, Si, B can exist stably in the fcc-Fe/Cr2O3 interface system, Mo and Ni tend to be on the side of the interface matrix, Mo has a tendency to diffuse into the oxide layer, Mn and Si are more inclined to be distributed in the oxide layer of the interface system, and B can stably exist on the side of the fcc-Fe/Cr2O3 interface matrix; the addition of B has different effects on the occupancy tendency of the four elements in the fcc-Fe/Cr2O3 interface system. B on the side of the interface matrix can inhibit the segregation of Mo to the side of the interface matrix, and promote the segregation of Mn to the side of the interface matrix, so that the distribution of Ni in the interface system tends to be uniform; the density of states when Mo is distributed on the interface shows that Mo has a strong interaction with O atoms in the interface, which improves the bonding force and stability between atoms at the interface; after Mo+B, Mn+B, Ni+B and Si+B are compositely dissolved into the fcc-Fe/ Cr2O3 interface system, the energy at the Fermi level is 42.34 states/eV, 44.65 states/eV, 43.99 states/eV and 42.30 states/eV, respectively. The 4d orbital electrons of Mo, the 3d orbital electrons of Mn and Ni and the 3p orbital electrons of Si provide the main contribution.