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采用基于密度泛函理论的第一性原理方法,计算了B2型FeAl金属间化合物的Fe8Al8和Fe8XAl7(X=Cr,Mo和W)超晶胞系统总能量、结合能、晶格常数、弹性常数、态密度和差分电荷密度,研究了合金元素对B2型FeAl金属间化合物晶体结构、电子结构和力学性能的影响。根据系统驰豫和几何优化确定了合金系统的稳定晶体结构;计算结果表明:随着加入元素原子半径的增大,合金的晶格常数相应增大,Fe8WAl7的晶格常数最大,Fe8CrAl7的晶格常数最小。Cr、Mo和W的加入均提升了FeAl的体模量、剪切模量和弹性模量以及改善了FeAl的脆性,其中Mo的加入对FeAl的脆性改善作用最大。根据电子结构和Cauchy压力参数计算结果的分析,FeAl金属间化合物为脆性相,主要原因是其电子结构中Fe的s、p、d态与Al的s、p态存在电子轨道杂化,呈明显的共价键特征。合金元素改善FeAl脆性的微观机理为:合金元素原子以d轨道电子为主参与了FeAl金属间化合物的电子杂化,增强了FeAl合金的结合能力;合金元素原子的加入使电荷转移量增加,增强了原子间离子键成分的作用,提高了FeAl合金的稳定性。
The first-principle method based on density functional theory (DFT) is used to calculate the total energy, the binding energy, the lattice constant and the elastic constant of Fe 8 Al 8 and Fe 8 X Al 7 (X = Cr, Mo and W) superlattice systems of type B2 FeAl intermetallic compounds , Density of states and differential charge density, the effects of alloying elements on the crystal structure, electronic structure and mechanical properties of B2 FeAl intermetallic compounds were studied. The stable crystal structure of the alloy system was determined according to the system relaxation and geometric optimization. The calculation results show that the lattice constant of the alloy increases with the increase of the atomic radius of Fe8WAl7, and the lattice constant of Fe8CrAl7 The minimum constant. The addition of Cr, Mo and W both enhanced the bulk modulus, shear modulus and elastic modulus of FeAl and improved the brittleness of FeAl. Mo addition had the greatest effect on improving the brittleness of FeAl. According to the calculation of the electronic structure and the Cauchy pressure parameter, the FeAl intermetallic compound is a brittle phase mainly due to the electronic orbital hybridization of the s, p and d states of Fe in the electronic structure with the s and p states of Al, The covalent bond features. The microscopic mechanism of alloying elements to improve the brittleness of FeAl is: the alloying element atoms mainly participate in the electron hybridization of FeAl intermetallics with d orbital electrons, which enhances the bonding ability of FeAl alloy; addition of alloying element atoms increases the charge transfer amount and enhances The role of the ionic bond between atoms to improve the stability of FeAl alloy.