First principle study of occupancy, bonding characteristics and alloying effect of Zr, Nb, V in bulk γ-Fe(C)

Abstract

The total energy, binding characteristics, density of states, charge distribution and differential charge density of γ-Fe(C)-M crystal cells formed by solid solution of Zr, Nb and V in γ-Fe(C) were calculated by using the first-principles method. Thus, the mechanism of Zr, Nb, and V with γ-Fe(C) was investigated in this paper. The results show that Zr, Nb and V all preferentially replaced the Fe atoms which are at the top angle in γ-Fe(C). Crystal cell reaches its highest stability after V solid solution. Nb reaches after it, and Zr is relatively weak. In the γ-Fe(C)-Zr cell, Fe-Zr covalent bond and Zr-C ionic bond are the main chemical bonds. In the γ-Fe(C)-Nb and γ-Fe(C)-V cells, Fe-Nb and Fe-V covalent bonds are the main chemical bonds with a number of Nb-C and V-C ionic bonds. After solid solution, the electron cloud density around C atom changed little, while Fe atom changed obviously. The orbital electrons around Fe atoms in γFe(C)-V has maximal distribution, which means that the electrons delocalized most and most of the electrons are bonding. It is the main factor for the increase in the binding energy of crystal cell. The effects of Zr, Nb, V solution on austenitic stability are investigated by studying the influence of alloy element on γFe(C) electronic structure.