LUIS AUGUSTO MENDES DOS REIS
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Resumo IPEN-doc 29424 Processing of zirconium sponge and zirconium alloys in an electric arc furnace2022 - REIS, L.A.; MORAIS, N.W.; BETINI, E.G.; PEREIRA, L.T.; POLITANO, R.; BARBOSA, L.P.; MARTINEZ, L.G.; MUCSI, C.S.; ROSSI, J.L.Zirconium and its alloys, as well as titanium and its alloys, are mostly used in the nuclear and aeronautical industries, respectively. A nuclear-grade zirconium sponge is the main component for obtaining nuclear fuel element cladding for nuclear power plants and other components, such as grids and springs. The zirconium sponge is also an important raw material in obtaining various alloys for nuclear fuels from small and medium power reactors, such as U-Zr-Nb. Thus, this project has relevance, since the clean melting of zirconium sponge will provide part of the domain of nuclear fuel technology. In this work, high entropy alloys (Ti-Zr-Nb-Ta-Fe-Cr) were produced in order to evaluate the evolution of the microstructure and modulus of elasticity as a function of temperature and heat treatment. A high entropy alloy with a composition different from those found in the literature is proposed. The materials were separated and melted in an electric arc furnace under a non-consumable electrode vacuum. These alloys were consolidated in the form of bars 220 mm long and thicknesses ranging from 8 to 12 mm. After melting, annealing was carried out at 1100 °C for 24 hours to homogenize the material obtained. The initial microstructural analyzes showed two very distinct phases with defined grain boundaries, the chemical etching to reveal the microstructure was a solution of 100 ml deionized H2O + 10 ml HNO3 + 2 ml HF. The samples are being quenched in oil and X-ray diffraction tests will be carried out in a hot chamber and the results will be presented at this congress.Resumo IPEN-doc 29406 Effect of shielding gas on thermal properties of thin plates of duplex stainless steel welded by pulsed GTAW process2022 - BETINI, E.G.; TERUI, C.; REIS, L.A.; MUCSI, C.S.; LUZ, T.d.; ORLANDO, M.T.; ROSSI, J.L.In this work, UNS32304 duplex stainless steel welds were evaluated by observing the influence of the pulsed GTAW welding process on thermal properties of this material. 1.8 mm duplex stainless steel sheets were welded by the GTAW process varying the shielding gases between pure Ar and Ar + 2%N2 without filler metal. The thermal welding cycles were studied by a type K and S thermocouple system fixed close to the welding line. The temperature distribution along the welding line was determined by reaching values within the phase transformation range of this material. Through a quantitative and semiquantitative evaluation of elements the Creq/Nieq ratio was calculated for the ferrite, austenite and secondary austenite grains of the solidified zone, ZAC and base metal. The addition of 2% N2 in the shielding gas caused an increase of the austenite formation in the solidified zone if compared to welding without N2 addition, being the most suitable atmosphere for welding in duplex stainless steels. The thermophysical properties were studied by laser flash method (MFL) used to determine the thermal diffusivity of the material in the thickness direction. The specific heat and Curie temperature of the solidified zone of welds was obtained by the thermal analysis by differential exploratory calorimetry (DSC). Measurements of porosities and specific mass of the solidified zone were obtained and compared with the base metal and metal as received. With this information it was possible to evaluate the thermal conductivity of the material after welding process. Increased thermal conductivity was found for both welded samples and suggest correlation with increased ferritic phase and decreased porosity also observed for solidified zone.Artigo IPEN-doc 27177 On the melting of zirconium alloys from scraps using electron beam and induction furnaces2020 - PEREIRA, LUIZ A.T.; MARTINEZ, LUIS G.; MUCSI, CRISTIANO S.; REIS, LUIS A.M. dos; ROSSI, JESUALDO L.The pressurized water reactor (PWR) employs UO2pellets as nuclear fuel, which are packedin zirconium alloy tubes called nuclear fuel cladding. In the manufacture of the nuclearfuel, machining scraps are generated which are not easily discarded as scraps because ofits high cost. These zirconium nuclear alloys are very costly and are not produced in Brazil.In this work, novel methods to recycle Zircaloy scraps using vacuum induction melting andelectron beam furnaces were used to obtain ingots. The cast ingots were subjected to ther-mal treatments and then chemically analyzed, followed by microstructural characterization,mechanical properties evaluation, and X-ray diffraction. The results indicated the feasibilityof the processes for obtaining alloys for application in the nuclear area, chemical industryor materials for biological applications such as dental prostheses.