The role of second phase particles and grain boundaries on recrystallization: Quasi-in situ experiments and modeling in U-10Mo alloy system

Abstract

Grain boundaries and second phase particles are known to have a significant influence on the recrystallization kinetics of metals undergoing thermomechanical processing. Using ex-situ heating methods and electron backscattered diffraction, we deconvoluted the influence of grain boundaries and second phase particles on the recrystallization kinetics in uranium alloyed with 10 wt% molybdenum (U-10Mo). The U-10Mo alloy is a monolithic nuclear fuel relevant to nuclear non-proliferation efforts. In this study, the sample was homogenized at 1173 K (900 °C) for 48 h, hot rolled to 20% reduction, and subsequently annealed at 873 K (600°C) in sequential increments to a total of 1320 min. It was observed that upon deformation, dislocations are accumulated in the vicinity of uranium carbides (UCs) which serve as nucleation sites for randomly oriented grains during annealing. Most nucleation occurred in the first 30 min of annealing and favored the grain boundaries and shear bands near the carbides. A simulation of recrystallization coupling the finite element method (FEM) and the Kinetic Monte Carlo Potts Model (KMCPM) was developed to investigate the grain structure evolution in the polycrystalline U-10Mo fuel. The observed U-10Mo recrystallization and grain growth kinetics with respect to time and temperature was quantitatively reproduced.