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基于固体与分子经验电子理论(EET),对Fe-Cr合金(Cr含量为0~30%,原子分数)的价电子结构进行了半定量分析,利用界面电子密度差Δρ的计算方法,计算了Fe-Cr合金与Cr₂O₃、Fe₂O₃钝化膜低指数晶面间的电子密度。结果表明,Fe-Cr合金固溶体的杂化原子轨道数σ_n、最强键共价电子数n_A和最强键键能E_A均大于纯Fe,Cr能提高Fe基体的稳定性。当Cr含量达到12.52%和24.3%时,Cr原子从低阶迁移到共价电子数少的高阶状态,不稳定性增加,此时Cr易偏离平衡位置与腐蚀介质作用形成钝化膜,造成Fe-12.52%Cr和Fe-24.3%Cr合金的耐腐蚀性能发生突变。Fe-Cr合金与Cr₂O₃、Fe₂O₃钝化膜的24个低指数界面中,只有Fe-Cr(112)/Cr₂O₃(0001)、Fe-Cr(112)/Cr₂O₃(101?0)_Cr、Fe-Cr(112)/Fe₂O₃(112?0)界面的Δρ <10%,对于同等Cr含量的基体,Fe-Cr(112)/Cr₂O₃(101?0)_Cr界面Δρ最小,满足Δρ<10%的杂化原子轨道数σ最大。随着基体中Cr含量升高,Fe-Cr(112)/Cr₂O₃(0001)和Fe-Cr(112)/Fe₂O₃(112?0)界面Δρ降低,σ增加,Cr₂O₃、Fe₂O₃与基体的界面更加稳定牢固,因此Fe-24.3%Cr合金的耐腐蚀性可跃迁至更高水平。价电子结构对Fe-Cr合金耐蚀性能变化的分析结果基本符合Tammann定律的描述。

Based on the empirical electron theory (EET) of solids and molecules, the valence electron structure caculation results of Fe-Cr alloy containing (0~30%)Cr were analyzed semi-quantitatively. The electron density differences of interface (Δρ) between Fe-Cr alloy and Cr₂O₃, Fe₂O₃ passivation films were calculated. According to the results, adding Cr to α-Fe matrix can strengthen the matrix by improving the number of hybid atomic orbitals σ_n, the number of the strongest bond covalent electron pairs n_A and the strongest covalent bond energy E_A of Fe-Cr alloy. Once the content of Cr rises up to 12.52% and 24.3%, the corrosion resistance of Fe-Cr alloy is improved because of Cr being changed to a higher hybrid level, where Cr becomes more unstable and easily reacts with environment to form a complete passivation layer of Cr₂O₃. Moreover, among the electronic density differences of 24 low-index faces between Fe-Cr and Cr₂O₃, Fe₂O₃, only the Δρ of Fe-Cr(112)/ Cr₂O₃(0001), Fe-Cr(112)/Cr₂O₃ (101?0)_Cr,Fe-Cr(112)/Fe₂O₃(112?0) are lower than 10%. For the matrix with same content of Cr, the Δρ between Fe-Cr(112) and Cr₂O₃(101?0)_Cr is the lowest, but the number of hybid atomic orbitals σ satisfied Δρ<10% is the largest. Δρ (σ) of Fe-Cr(112)/Cr₂O₃(0001) and Fe-Cr(112)/Fe₂O₃(112?0) is decreased (increased) with the increase of Cr, therefore the interface bonding strength between Cr₂O₃, Fe₂O₃ and matrix will be enhanced, it has been found that the corrosion resistance of Fe-24.3%Cr is better. The calculation results of variation of Fe-Cr corrosion resistance with Cr content are in better agreement with Tammann's law.