Ti,C,N在α-Fe基中的合金化效应及对键合性质的影响

The alloying of Ti,C,N in bulk a-Fe and their effects on bond characters

基于第一性原理赝势平面波方法研究了合金元素Ti,C,N对α-Fe基电子结构及键合性质的影响,计算了含Ti,C,N的Fe基固溶体的总能量、结合能,分析了态密度、电荷布居数、交叠布居数和电荷密度,从理论上解释了在Fe基中固溶Ti,C,N后其性能改善的原因.结果表明,随着Fe基固溶体中Ti(0—12.5 at%),C(0—11.11 at%),N(0—11.11 at%)含量增加,结合能略有增加;Ti,C,N的固溶使各Fe基固溶体在费米能级处强烈成键,结合能力增强,并且在费米能级附近出现赝能隙,表明固溶体中金属键与共价键共存;随着Ti,C,N含量的增加,C,N分别与Ti,Fe之间的共价键结合强度加强,部分C,N原子会与Ti原子结合形成TiC,TiN颗粒,起到沉积相颗粒强韧化作用.

The electronic structures and the bond characters of bulk a-Fe with Ti, C, N additions are studied using the first-principls pseudopotential plane-wave method. The total energy and the cohesive energy are calculated, and the Mulliken population, the overlap population, the density of states and the charge density are also analyzed, which can give a microscopic reason why the mechanical property is improved after the infiltration of Ti, C, N into bulk Fe. The calculated results show that with the alloying element Ti（0-12.5 at%）, C（0-11.11 at%）, N（0-11.11 at%） contents increasing, the cohesive energy of alloy increases slowly and the structure keeps stable. The additions of Ti, C, N into the alloy enhance the reciprocal hybridization in Fermi energy level, and the binding abilities of Ti, C, N, Fe become stronger. The pseudo-gap near the Fermi energy level means the coexistence of covalent and metallic bonds in alloy. With the contents of alloying elements increasing, the covalent bondings between C, N and Ti, Fe become stronger, and part of C and N atoms will be bound to Ti atoms and form TiC and TiN particles, thereby strengthening the dispersion.