Diffusion of vacancy–solute complexes in alloys

Some non-equilibrium kinetic processes, such as thermal non-equilibrium segregation and deformation induced non-equilibrium segregation, require the presence of vacancy–solute complexes to be part of the underlying mechanism. To theoretically evaluate these processes, knowledge of the diffusivity for the complexes is required. Because it is difficult to experimentally measure this diffusivity, mechanisms for the complex diffusion are theoretically described for both fcc and bcc crystals. The activation energies involved in the complex diffusion are in turn estimated for the fcc γ-Fe and bcc α-Fe matrices on the basis of these mechanisms and some available data such as vacancy migration energies, solute diffusion activation energies and vacancy–solute binding energies.