Electronic structures and mechanical properties of metal doped α-Fe (N): a first principle calculation

The binding energies, electronic structures and mechanical properties of M doped in α-Fe(N) system were investigated by using first principle calculations, where M represents Ti, V, Cr, Mn, Co,and Ni. The results show that Ti and V occupy preferentially the corner of α-Fe(N) unit cell, Cr and Mn occupy preferentially the body-centered position of the cell, the structure is the most stable when Co and Ni are not adjacent to the N atom. The doped elements Ti and V strengthen the stability of α-Fe(N); Cr, Mn and Ni have an opposite effect; Co does not affect the stability. The metallic and ionic bonds coexist in the doped systems. The bonding orbitals are created by the interaction of M3d, Fe4s3p3d and N2p. Compared with the pure α-Fe system, the material rigidity is stronger for doped systems. The calculation results show that the elastic modulus E,shear modulus G and bulk modulus B of α-Fe(N)-V are the maximum. It reveals that doped V can significantly improve the overall mechanical properties of steel and it is the most effective nitrogen fixing element. It is consistent with the experimental results of high nitrogen steel smelting.