Kinetic pathways from embedded-atom-method potentials: Influence of the activation barriers

Abstract

The precipitation kinetics in alloys is now widely studied at a microscopic scale, using Monte Carlo simulations and simple energetic and diffusion models. In the present paper, we first test the assumptions of these models, in the case of the copper precipitation in α-iron, using static relaxation of a many-body embedded-atom-method (EAM) potential. In dilute alloys, the EAM configurational energies can be described by simple pair interactions on rigid lattice. The EAM vacancy migration barriers are reproduced by saddle-point binding energies which are very sensitive to both the nature of the jumping atom and that of the first neighbors of the saddle point. Finally, these microscopic parameters are integrated in a Monte Carlo scheme. The dependence of the saddle-point binding energies on the local atomic configurations modifies the relative mobility of small Cu clusters and Cu monomers. At high temperature, it leads to a slowing down of the precipitation by a constant ratio of on the time scale, but at low temperature, the kinetic pathway is dramatically modified.