GUILHERME FERNANDES NIELSEN
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Tese IPEN-doc 28038 Texturas cristalogrĆ”ficas em ligas de urĆ¢nio-molibdĆŖnio laminadas a quente e recozidas2021 - NIELSEN, GUILHERME F.As ligas do sistema urĆ¢nio-molibdĆŖnio tĆŖm um grande potencial para serem usadas como combustĆvel monolĆtico em reatores nucleares de testes, pesquisas e tambĆ©m de potĆŖncia de pequeno porte. A laminaĆ§Ć£o e alguns tratamentos tĆ©rmicos sĆ£o processos normalmente usados para a produĆ§Ć£o de combustĆveis monolĆticos. Durante o processamento dos combustĆveis monolĆticos, ocorre o fenĆ“meno da textura cristalogrĆ”fica, que pode alterar suas propriedades isotrĆ³picas. Baseando-se nesse contexto, este trabalho abordou os fenĆ“menos de orientaĆ§Ć£o cristalogrĆ”fica preferencial em ligas do sistema urĆ¢nio-molibdĆŖnio laminadas a quente e recozidas. As ligas fundidas no forno de induĆ§Ć£o U7,4Mo e U9,5Mo foram tratadas para homogeneizaĆ§Ć£o, laminadas a quente e recozidas. Nestas etapas de processo, as ligas foram caracterizadas microestruturalmente por tĆ©cnicas de microscopia Ć³tica e eletrĆ“nica. A presenƧa de fases cristalinas e a macrotextura foi analisada por difraĆ§Ć£o de raios X. A microtextura foi caracterizada por difraĆ§Ć£o de elĆ©trons retroespalhados, EBSD. As ligas no estado bruto de fusĆ£o e processadas apresentaram fase Ī³. A melhor condiĆ§Ć£o de homogeneizaĆ§Ć£o foi a 1000 ĀŗC por 5 horas. As ligas de urĆ¢nio deformadas apresentaram fibras Ī±, Ī³ e Īø. A intensidade destas fibras variou em funĆ§Ć£o do grau de deformaĆ§Ć£o. Foi notada que a nucleaĆ§Ć£o de grĆ£os recristalizados ocorreu em locais preferenciais. Os grĆ£os recristalizados possuem orientaĆ§Ć£o preferencial. No recozimento, foi possĆvel verificar que a microestrutura das amostras recozidas varia de acordo com o grau de deformaĆ§Ć£o e do tempo de recozimento. A deformaĆ§Ć£o gerou contornos de especiais do tipo CSL (coincidence site lattice) e sua movimentaĆ§Ć£o foi observada com o recozimento.Artigo IPEN-doc 27721 Crystallographic texture of hot rolled uranium-molybdenum alloys2020 - NIELSEN, G.F.; MORAIS, N.W.S.; LIMA, N.B.The uranium molybdenum (U-Mo) alloys have the potential to be used as low enriched uranium nuclear fuel in research, test, and power nuclear reactors. U-Mo alloy with composition between 7 and 10 wt% molybdenum shows excellent body centered cubic phase (Ī³ phase) stabilization and presents a good nuclear fuel testing performance. Hot rolling is commonly utilized to produce nuclear fuel plate where it promotes the cladding and the fuel alloy bonding. The mechanical deformation generates crystallographic preferential orientation, the texture, which influences the material properties. This work studied the texture evolution in hot rolled U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace, homogenized at 1000Ā°C for 5 h, and then hot rolled at 650Ā°C in three height reductions: 50, 65 and 80%. The crystalline phases and the texture were evaluated by X-ray diffraction (XRD). The as-cast and processed alloys microstructures were characterized by optical and electronic microscopies. The as-cast, homogenized, and deformed alloys have the Ī³ phase. It was found microstructural differences between the U7.4Mo and U9.5Mo alloys. The homogenized treatment showed effective for microsegregation reduction and was not observed substantial grain size increasing. The deformed uranium molybdenum alloys presented Ī±, Ī³, Īø texture fibers. The intensity of these texture fibers changes with rolling reduction.Artigo IPEN-doc 26358 Crystallographic texture of hot rolled uranium-molybdenum alloys2019 - NIELSEN, GUILHERME F.; MORAIS, NATHANAEL W.S.; SILVA, SELMA L.; LIMA, NELSON B. deThe uranium molybdenum (U-Mo) alloys have potential to be used as low enriched uranium nuclear fuel in research, test and power nuclear reactors. U-Mo alloy with composition between 7 and 10 wt% molybdenum shows excellent body centered cubic phase (Ī³ phase) stabilization and presents a good nuclear fuel testing performance. Hot rolling is commonly utilized to produce parallel fuel plate where it promotes bonding the cladding and the fuel alloy. The mechanical deformation generates crystallographic preferential orientation, the texture, which influences the material properties. This work studied the texture evolution in hot rolled U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace, homogenized at 1000Ā°C for 5 h and then hot rolled at 650Ā°C in three height reductions: 50, 65 and 80%. The as-cast and processed alloys microstructures were characterized by optical and electronic microscopies. The crystalline phases and the texture were evaluated by X-ray diffraction (XRD). The as-cast, homogenized and deformed alloys have Ī³ phase. It was found microstructural differences between the U7.4Mo and U9.5Mo alloys. The homogenized treatment showed effective for microsegregation reduction and were not observed substantial grain size increasing. The deformed uranium molybdenum alloys presented strong Ī³ fiber texture (111) and moderated Ī±-fiber texture (hkl) <110>.