The Improvement Of Phase-field Method And Its Application

The origin of this study comes from the Phase-field simulation of irradiation effect for nuclear materials.In order to coincide with the experimental parameters,it's found that there are some problems in the traditional phase field simulation process,for example,in the void evolution process,the vacancy concentration is ultra-low and the solution of the Cahn-Hilliard equation for traditional phase-field method is complicated.The traditional method usually use Landau polynomial and diffuse-interface model to represent chemical free energy and interface energy respectively,and it is difficult to obtain the appropriate Landau coefficients fitting for the ultra-low concentration of vacancies in the real irradiation condition.This impetus us to develop a new reaction-diffusion phase-field model to deal with low concentration problem.Based on the Rate-theory and inspiration of the phase-field model for lithium dendrite growth,we developed a new reaction-diffusion phase field model with steep solute interface.In this new model,the nucleation process is treated as reaction of new phase and solute at the interface and the diffusion equation is modified to add a reaction term.We applied the model to the field of irradiation damage,studied the nucleation and growth of void under different irradiation damage,the void evolution in polycrystalline system,the effect of irradiation depth,3D irradiation simulation and the interface effect.It's found that in the field of irradiation damage,our model is fine to prevent disadvantages of traditional models,the vacancy concentration may close to the real experimental data and the time scale in the simulation was greatly improved.After that,the phase field method can be extended to the system with long-range elastic interaction system.we used the model to study the evolution of hydride and the multicomponent alloy growth systems,the inhomogeneous morphology of precipitates were obtained.Based on the reaction-diffusion phase-field model,we also developed a new phase-field potential table method,makes the phase field model full digital,getting rid of the difficulties of fitting coefficients.Finally,we developed a parallel package for phase-field calculation based on MPI and GPU,which is easy to develop and contain a long-range interaction solver.It provides a more convenient tool for large-scale and high-precision phase-field calculations.We use the package to study the large scale vortex evolution in multiferroic materials and the concentration evolution of magnetic particle in polymer liquid,the results are consistent with the experiments.