Patterning in systems driven by nonlocal external forces

Radiation-Induced Patterning at the Nanometric Scale: A Phase Field Approach

The phase field approach was developed in the last 20 years to handle radiation damage in materials. This approach bridges the gap between atomistic simulations extensively used to model first step of radiation damage at short time and continuum approach at large time. The main advantage of such an approach lies in its ability to compute not only the microstructure at the nanometric scale but also to calculate generalized susceptibilities such as elastic constants under irradiation. After a brief description of the rate theory, used to model the microstructure induced by irradiation, we briefly discuss the foundation of the phase field method, highlighting not only its advantages, but also its limitations in comparison with the rate theory. We conclude this presentation by proposing future orientations for computing the microstructure in irradiated materials.

Symmetry Breaking Resulting from Long-Range Interactions in Out of Equilibrium Systems: Elastic Properties of Irradiated AgCu

This work presents a consistent formulation of the phase-field approach to model the behavior of nonmiscible alloys under irradiation which includes elastic strain fields, an example of a long-range interaction. Simulations show that the spatial isotropy that is characteristic of radiation-induced patterns breaks down as a result of the elastic strain energy. The consequence of this is the emergence of superlattice structures under irradiation liable to modify macroscopic material properties. This approach is assessed against the experimental study of a AgCu alloy under irradiation: we compare our simulation results to measured solubility limits and Young moduli.

Predicting Nonequilibrium Patterns beyond Thermodynamic Concepts: Application to Radiation-Induced Microstructures

In this work, we derive an analytical model to predict the appearance of all possible radiation-induced steady states and their associated microstructures in immiscible A_{c[over ¯]}B_{1-c[over ¯]} alloys, an example of a nonequilibrium dynamical system. This model is assessed against numerical simulations and experimental results which show that different microstructures characterized by the patterning of A-rich precipitates can emerge under irradiation. We demonstrate that the steady-state microstructure is governed by irradiation conditions and also by the average initial concentration of the alloy c[over ¯]. Such a dependence offers new leverage for tailoring materials with specific microstructures overcoming limitations imposed by the equilibrium thermodynamic phase diagram.

Irradiation-based design of mechanically resistant microstructures tuned via multiscale phase-field modeling

We present a multi-scale phase field modeling of stationary microstructures produced under 1 MeV krypton ion irradiation in a phase separating concentrated solid solution of silver and copper. We show that the mixture reaches ultimately a stationary micro-structural state made of phase domains with composition and size distribution mapped to the values of the incident flux of particles and of the temperature, variables that help defining a non equilibrium phase-diagram for the irradiated alloy. The modeling predicts the formation of diverse microstructures likely connected to spinodal hardening, thus opening the perspective of the on-purpose tuning of mechanically resistant microstructures and the preparation of metastable alloys with mechanical properties improved by comparison to counterparts obtained via classical thermo-mechanical treatments.