摘要
采用第一性原理的方法计算了Ti、Nb、Zr固溶于γ-Fe-(B)后形成晶胞的体积变化率、晶胞总能、结合能、态密度、差分电荷密度、迁移激活能及力学性能,并由此研究了Ti、Nb、Zr与γ-Fe-(B)的微观作用机理。结果表明,3种原子均优先取代γ-Fe-(B)晶胞中顶角位置的Fe原子。Ti掺杂后,γ-Fe-(B)的结合能降低,B原子的迁移激活能降低,B原子可能更容易偏聚。Nb、Zr掺杂后,γ-Fe-(B)的结合能升高,增加γ-Fe-(B)的稳定性。Zr对于提高γ-Fe-(B)稳定性的作用要大于Nb固溶。γ-Fe-(B)晶胞中,主要以离子键为主,并伴随少量的共价键;γ-Fe-(B)-Ti晶胞中主要形成的是较弱的离子键;而γ-Fe-(B)-Nb、γ-Fe-(B)-Zr晶胞中主要形成的是较强的共价键。M、Fe、B均提供成键电子,参与成键的是Md、Fe3d和B2p轨道。γ-Fe-(B)-Ti晶胞中Ti3d电子相对比较局域,参与成键的作用较弱,γ-Fe-(B)-Nb及γ-Fe-(B)-Zr晶胞中Nb4d电子及Zr4d电子离域性较强,成键能力较强。Ti、Nb、Zr均能提高γ-Fe-(B)的力学性能,主要表现为硬度及抗压强度有所提高,但塑性及韧性变化不大。Zr对于提升体系硬度的作用效果是最明显的。论文依据合金元素对γ-Fe-(B)电子结构的影响,探讨了Ti、Nb、Zr及B原子对于提高材料淬透性的影响机制。
The volume change rate, total cell energy, binding characteristics, state density, differential charge density, migration activation energy and mechanical properties of cells formed by solid solution of Ti, Nb and Zr in γ-Fe-(B) were calculated by first-principles method, and the microscopic mechanism of the interaction of Ti, Nb, Zr with γ-Fe-(B) was studied. The results show that the three kinds of atoms all preferentially replace the Fe atoms at the apex angle in γ-Fe-(B) cells. After Ti doping, the binding energy of γ-Fe-(B) decreases, migration activation energy of B atoms reduces, and B atoms may be more likely to segregate. After Nb or Zr doping, the binding energy of γ-Fe-(B) increases, resulting in the increasing stability of γ-Fe-(B). The effect of Zr on improving γ-Fe-(B) stability is greater than that of Nb. In the γ-Fe-(B) cell, ionic bonds are mainly formed, and accompanied by a small amount of covalent bonds;weak ionic bonds are mainly formed in the γ-Fe-(B)-Ti cell, while strong covalent bonds are formed in the γ-Fe-(B)-Nb and γ-Fe-(B)-Zr cells. All M, Fe, and B atoms can provide bonding electrons, and the Md, Fe3 d, and B2 p orbitals are involved in bonding. The Ti3 d electrons in the γ-Fe-(B)-Ti are relatively localized, and thus the effect of bonding is relatively weak. Electron delocalization effect of Nb4 d and Zr4 d electrons in the γ-Fe-(B)-Nb and γ-Fe-(B)-Zr cells are strong, resulting in a strong bonding ability. The Ti, Nb, and Zr doping can all improve the mechanical properties of γ-Fe-(B), in which the hardness and compressive strength obviously increase, but the plasticity and toughness change little. The effect of Zr on increasing the hardness of the system is the biggest. Based on the influence of alloying elements on the electronic structure of γ-Fe-(B), the influence mechanism of Ti, Nb, Zr and B atoms on improving the hardenability of the material is discussed.
作者
刘飞
LIU Fei(Department of Mechanical Engineering,Zhonghuan Information College,Tianjin University of Technology,Tianjin 300380,China)
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2021年第5期178-186,共9页
Transactions of Materials and Heat Treatment
基金
天津市教委科研计划(2019KJ157)。
