A review: applications of the phase field method in predicting microstructure and property evolution of irradiated nuclear materials

Yulan Li,Shenyang Hu,Marius Stan,Xin Sun

doi:10.1038/s41524-017-0018-y

Abstract

Complex microstructure changes occur in nuclear fuel and structural materials due to the extreme environments of intense irradiation and high temperature. This paper evaluates the role of the phase field method in predicting the microstructure evolution of irradiated nuclear materials and the impact on their mechanical, thermal, and magnetic properties. The paper starts with an overview of the important physical mechanisms of defect evolution and the significant gaps in simulating microstructure evolution in irradiated nuclear materials. Then, the phase field method is introduced as a powerful and predictive tool and its applications to microstructure and property evolution in irradiated nuclear materials are reviewed. The review shows that (1) Phase field models can correctly describe important phenomena such as spatial-dependent generation, migration, and recombination of defects, radiation-induced dissolution, the Soret effect, strong interfacial energy anisotropy, and elastic interaction; (2) The phase field method can qualitatively and quantitatively simulate two-dimensional and three-dimensional microstructure evolution, including radiation-induced segregation, second phase nucleation, void migration, void and gas bubble superlattice formation, interstitial loop evolution, hydrate formation, and grain growth, and (3) The Phase field method correctly predicts the relationships between microstructures and properties. The final section is dedicated to a discussion of the strengths and limitations of the phase field method, as applied to irradiation effects in nuclear materials.

Highlights

High energy particle radiation can create major changes in the shape and thermo-mechanical properties of nuclear fuels and structural components of nuclear reactors
The main effects of radiation on reactor materials are: (1) dimensional change associated with gas bubble swelling, void swelling, grain growth, and creep;[1,2,3,4,5] (2) loss of ductility and increase in ductile-brittle transition temperature (DBTT) due to the formation of secondphase precipitates, self-interstitial atomic (SIA) loops, and dislocation networks;[6, 7] (3) oxidation and corrosion accelerated by high temperature, fission products, and radiation damage;[8,9,10] and (4) local and bulk changes in chemical composition, including irradiation-enhanced segregation of alloy components and phase separation.[11,12,13,14,15,16,17]
The phase field (PF) method is based on the fundamental thermodynamic laws, the kinetics of defects in the system under examination, and the understanding of the mechanisms behind the material processes

Summary

INTRODUCTION

The irradiated material’s microstructure is inherently inhomogeneous in composition and features.[46]. Grain growth and recrystallization are important features that occur in irradiated nuclear materials and has been investigated with the PF method in nuclear fuels UO2 and U-7Mo.[91,92,93,94,95] These modeling expanded the pure grain growth model developed by Chen and Yang[120] with accounting for the effects of pore/void or gas bubble pinning,[91, 92] temperature gradient effect,[93] initial grain structure,[94] and dislocation density,[95] respectively. It is crucial to have the spatial evolution of dislocation density in order to model the radiation-induced recrystallization and recrystallization kinetics

Mij j δF δcj þ ξi þ

CONCLUSIONS