It was recalled that, in previous studies of phase separation in alloys under irradiation, two surprising results had been observed: alloys could exhibit a compositional pattern whose amplitude and wavelength were unchanged after long aging, and phase separation could occur at temperatures well above the coherent spinodal. A model of phase-separation kinetics in systems exposed to energetic particle irradiation extended here so as to include the effects of mobile dislocations. It was shown that, by combining the Enrique-Bellon model of spinodal decomposition under irradiation with the Haataja-Leonard model of mobile dislocations, both of these experimental observations could be explained. The combined model consisted of coupled kinetic equations which described the evolution of the composition field and the Airy stress function arising from dislocation-dislocation interactions. It was shown that when dislocations were allowed to participate in the decomposition reaction, phase separation could occur at temperatures above the coherent spinodal; in agreement with several experiments on irradiated alloys. A linear stability analysis of the governing kinetic equations was performed and three regimes of microstructural evolution were identified within the parameter space of damage cascade size versus incident flux: complete phase separation, solid-solution behaviour, and compositional patterning. In addition, numerical simulations of the evolving dislocation density and composition fields were performed. The numerical results provided the amplitude and wavelength of the stable patterns that could form under irradiation and elucidated the role played by misfit dislocations in reducing the coherency strain due to atom-size mismatch.

Continuum Model of Irradiation-Induced Spinodal Decomposition in the Presence of Dislocations. J.J.Hoyt, M.Haataja: Physical Review B, 2011, 83[17], 174106