Abstract

The structure stability, mechanical properties and electronic structures of B2-FeAl intermetallics and the influence of La/Ce doping were investigated by first-principles density functional theory calculations. Several models were established. The total energies, cohesive energies, lattice constants, elastic constants, electronic density of states of Fe₈Al₈ and Fe₈Al₇X (X = La, Ce) were analyzed. The stability of alloy systems were determined according to the cohesive energy results. The calculated lattice constants of Fe₈Al₇X (X = La, Ce) were found to be related to the atomic radii of the alloy elements. The calculation and analysis of the elastic constants showed that ductility of B2-FeAl can be improved by the addition of La or Ce, the order of the ductility was as follows: Fe₈Al₇Ce > Fe₈Al₇La > Fe₈Al₈. The results of electronic structures showed that the brittleness of B2-FeAl was mainly due to the orbital hybridization of the d orbital of Fe and p orbital of Al, showing typical characteristics of a valent bond. Specifically, the mechanism for improving the ductility of B2-FeAl is that d orbital of La/Ce is mainly involved in the hybridization of B2-FeAl.

摘要

通过第一性原理密度泛函理论计算，研究了B2-FeAl金属间化合物的结构稳定性，力学性能和电子结构，以及La / Ce掺杂的影响。建立了几种模型。分析了Fe ₈ Al ₈和Fe ₈ Al ₇ X（X = La，Ce）的总能量，内聚能，晶格常数，弹性常数，电子态密度。根据内聚能结果确定合金体系的稳定性。Fe ₈ Al ₇的计算晶格常数X（X = La，Ce）被发现与合金元素的原子半径有关。弹性常数的计算和分析表明，通过添加La或Ce可以提高B2-FeAl的延展性，其延展顺序为：Fe ₈ Al ₇ Ce> Fe ₈ Al ₇ La> Fe ₈ Al ₈。电子结构的结果表明，B2-FeAl的脆性主要归因于Fe的d轨道和Al的p轨道的轨道杂化，表现出典型的价键特性。具体地，提高B2-FeAl的延展性的机制是La / Ce的d轨道主要参与B2-FeAl的杂交。