Prediction of irradiation induced microstructures using a multiscale method coupling atomistic and phase field modeling: Application to the AgCu model alloy

Abstract

Microstructure patterning using the ion beam mixing process results from the competition between thermal diffusion and ballistic disordering induced by impinging ions. Although microstructure patterning under irradiation is now qualitatively understood, so far, no study could quantitatively estimate irradiation conditions leading to patterning. In this work, a new multiscale approach based on phase field was developed to simulate the microstructure evolution, and the occurrence of patterning due to ion irradiation in a silver-copper alloy, from atomic to microstructural scale. For that purpose, an efficient numerical scheme was developed to simulate the microstructure dynamics, within the framework of phase field. Equilibrium parameters of AgCu were computed using a mixed Monte Carlo-molecular dynamics approach. Ballistic effects induced by krypton ion irradiation, and point defect recreation leading to irradiation enhanced diffusion, were estimated using the binary collision approximation framework. As a result, we predicted the range of temperatures and irradiation fluxes leading to the formation of patterned microstructures in the AgCu alloy under krypton ion irradiation. Results were summarized in a pseudo phase diagram in the temperature-flux plane. Our model was in good agreement with a previous diffraction experimental study.