Effect of irradiation-induced cascade mixing on spinodal decomposition in U-Nb and U-Zr alloys: a phase field study

The spinodal decomposition of the γ-phase in U-Nb and U-Zr alloys under irradiation was investigated using the phase-field method coupled with micro-elasticity theory and rate dependent cascade mixing model. Microstructure evolutions of spinodal decomposition in U-Nb and U-Zr alloys were simulated by considering different initial compositions and dose rates. The volume fraction and composition distribution under different cascade mixing were presented. The simulation results show that the volume fractions and equilibrium composition of the (Nb,Zr)-rich γ₂-phase and the rate of spinodal decomposition are influenced by the dose rate and initial alloy composition. The cascade mixing can drive Nb or Zr atoms back into solution until a new equilibrium state between local cascade mixing and spinodal decomposition is reached. The evolution analysis indicated that irradiation-induced cascade mixing acts in opposition to thermodynamically driven spontaneous spinodal decomposition, which can not only slow down the spinodal decomposition but also reduces the composition range of the miscibility gap.