Recrystallization and Grain Growth Simulations for Multiple-Pass Rolling and Annealing of U-10Mo
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Recrystallization and Grain Growth Simulations for Multiple-Pass Rolling and Annealing of U-10Mo WILLIAM FRAZIER, CHAO WANG, ZHIJIE XU, NICOLE OVERMAN, SHENYANG HU, and VINEET V. JOSHI A simulation model of recrystallization and grain growth has been developed to investigate grain structure evolution during deformation and heat treatment in polycrystalline U-10 wt pct Mo (U-10Mo) fuel. Experimentally obtained U-10Mo post-homogenization microstructures were used as input for closed-loop simulations of multiple rolling passes, intermediate heating, and final annealing. Finite element model calculations of deformation and Potts model simulations of recrystallization and grain growth were used to iteratively inform each subsequent stage of simulation. The model was then applied to predict the grain structure evolution during multiple-pass hot rolling and annealing of U-10Mo and benchmarked against experimentally observed U-10Mo recrystallization behavior. The results showed that our model was able to capture the coupling between deformation and recrystallization as a function of microstructure, including particle stimulated nucleation and recrystallization nucleation on grain boundaries. Additionally, we have achieved reasonable quantitative agreement with U-10Mo recrystallization and grain growth behavior. https://doi.org/10.1007/s11661-019-05582-6 The Minerals, Metals & Materials Society and ASM International 2019
I.
INTRODUCTION
THE U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA) has an ongoing effort to convert five civilian-use US high-performance research reactors (USHPRRs) from using highly enriched uranium to using less enriched uranium. Uranium alloyed with 10 wt pct Mo (U-10Mo) alloys have high uranium density even as LEU fuel, excellent irradiation resistance, and good thermal conductivity.[1–3] U-10Mo is used as a single foil sandwiched between aluminum cladding and a Zr interlayer, and is known as ‘‘monolithic’’ fuel. Typically, the U-10Mo foils are made by casting LEU and Mo into plates 0.2 inches thick, homogenizing the plates, hot rolling the plates to bond the Zr interlayer to U-10Mo and cold-rolled to their final thickness (typically 0.025 inches to 0.0085 inches. The foils are clad in aluminum by a hot isostatic pressing (HIP) step to form a fuel plate. It is
WILLIAM FRAZIER, CHAO WANG, ZHIJIE XU, NICOLE OVERMAN, SHENYANG HU, and VINEET V. JOSHI are with the Pacific Northwest National Laboratory, P. O. Box 999, Richland, WA, 99352. Contact e-mail: [email protected] Manuscript submitted August 20, 2019
METALLURGICAL AND MATERIALS TRANSACTIONS A
imperative that fuel fabrication should allow for strong control over the dimensions (e.g., U-10Mo and Zr interlayer thickness) of the final formed product and microstructure over a range of feedstock impurities (e.g., carbon), to not only meet the specifications but also minimize the losses associated with yield. It has been observed that the presence of the large grains in the as-cast and homogenized microstructure resu
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