Texturas cristalográficas em ligas de urânio-molibdênio laminadas a quente e recozidas

Abstract

NIELSEN, Guilherme F. Crystallographic texture of hot rolled and annealed uranium-molybdenum alloys. 2021. 144 p. Tese (Doutorado em Tecnologia Nuclear) -Instituto de Pesquisas Energéticas e Nucleares -IPEN/CNEN/SP. São Paulo.The Uranium-molybdenum alloys are a good candidate to be used as monolithic nuclear fuel in research, test, and also small power energy nuclear reactors. Hot rolling and annealing processes have been used for the production of monolithic fuels. The fuel production processes can generate crystallographic texture, which can modify the isotropic properties. Based on this, this work studied the preferred crystallographic orientation in hot rolled and annealed U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace and then homogenized, hot rolled, and annealed. The alloys were characterized by optical and electronic microscopies. The crystalline phases were identified by X-ray diffraction. The macrotexture was analyzed by x-ray diffractometry and the microtexture was characterized by EBSD. The as-cast and processed alloys have the gamma phase.The best homogenization condition achieved was 1000 °C for 5 hours. The homogenized treatment showed effective for microsegregation reduction and substantial grain size increase was not observed. The deformed uraniummolybdenum alloys presented α, γ e θ fibers. The intensity of these texture fibers changed with rolling reduction. It was noted that the nucleation of recrystallized grains occurred in preferred locations. Recrystallized grains have crystallographic texture. Upon annealing, it was possible to verify that the microstructure in the annealed samples varies according to the degree of deformation and the annealing time. The deformation generated coincidence site lattice (CSL) grain boundaries.The movement of these special boundaries was observed with annealing.