Fe self-diffusion and Cu and Ni diffusion in bulk and grain boundary of Fe: A molecular dynamics study

Segregation of solute elements or impurities to the grain boundary (GB) may be impeding the dislocation movement to cause the embrittlement of materials. The diffusion behaviour of elements in alloy, especially in GB, has a crucial effect on the segregation of impurities. We calculated the migration energy of Fe, Cu and Ni atom in Fe by the molecular dynamics method with the Nudged Elastic Band (NEB) method. The self-diffusion migration energy of Fe is 0.628 eV. The migration energies of Cu and Ni in Fe crystal are 0.592 eV and 0.608 eV, respectively. These results are good agreement with other calculations. The migration energies of Fe atom, Cu and Ni solute diffusion in [0 0 1] and [3 1 0] direction in GB Sigma 5 [3 1 0] and diffusion out GB Sigma 5 [3 1 0] in 11 1 1] direction are calculated. The Cu solute is segregate easier to GB and more difficult diffusion out of GB than the Ni solute. The Fe atom, Cu and Ni solute are very difficult to diffuse in [0 0 1] and [3 1 0] in Sigma 5 [3 1 0] because of their large migration energies, respectively. They can jump out of GB in [1 1 1] and back to GB in other [1 1 1] to diffuse near GB. (C) 2013 Elsevier B.V. All rights reserved.