ARMANDO CIRILO DE SOUZA
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Artigo IPEN-doc 28172 Microstructural evolution of the refractory WCuNi metallic alloy2021 - SOUZA, ARMANDO C.; ROSSI, JESUALDO L.; TSAKIROPOULOS, PANOS; ARISTONE, FLAVIOScience and technology of materials are widely interested in the development of new alloys involving tungsten due to its large applicability to the domain of nuclear material transportation. Tungsten is a refractory material and it has many applications in the nuclear industry due to its mechanical properties and excellent cross-section for thermal neutrons, being widely used for shielding of high-energy radiation. Some of the main elements added to tungsten forming alloys are Nb, Cr, Cu, Fe, Ni, Mo, Co, Sn, Ti, and Ta, which are responsible for modifications of the physical and chemical properties of the resulting alloy, interfering on the attenuation of gamma radiation. The main goal of this paper is to present a refractory alloy based on tungsten with embedded infiltrating elements like copper (Cu) and nickel (Ni) and characterize the microstructural evolution of different sintering process during its formation. Such a refractory alloy is submitted to the following characterization process: X-rays diffractometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy, and energy dispersive spectroscopy. The diffractometry exhibit typical standard results for the precursor powders: W, Cu, and Ni demonstrating high degrees of purity accordingly to the crystallographic determined parameters. The TGA for the powder W demonstrated thermal stability until 360 ºC, after an increase of mass due to the process of oxidation. The DSC analyze present two endothermal processes at temperatures 350 °C and 450 °C. The microstructural evolution of WCuNi samples presents the absence of oxidation, homogeneous morphology and stability of the binary phase α–β (W and CuNi respectively) for different sintering. These results shall be taken into consideration for future works, particularly on the study of shielding and gamma radiation attenuation.Artigo IPEN-doc 25793 Microstructural characterization of Zr1Nb alloy after hot rolling2019 - SOUZA, ARMANDO C.; ARISTONE, FLAVIO; ROSSI, JESUALDO L.; MARTINEZ, LUIS G.; CIONE, FRANCISCO C.; TSAKIROPOULOS, PANOS; GRANDINI, CARLOS R.; SILVA, WALLACE F. daThe nuclear industries have large interest on the development of new alloys involving zirconium (Zr) because this material presents extraordinary mechanical properties, outstanding resistance to corrosion and high permeability to thermal neutrons, being suitable for applications in areas such as energy and human health. The alloy studied in this paper is formed by Zr and niobium (Nb), normally expressed as Zr1Nb. These two elements have large chemical affinities with oxygen, carbon, and nitrogen, elements that normally are responsible for a series of damages in the alloy. The principal goal of this work is to obtain Zr1Nb alloys and to perform microstructural characterizations before and after the hot rolling process. The resulting alloys were subjected to a process of heat treatment, the temperature was increased at a rate of 10 K/min up to 1273 K and maintained for 2 h, after which it was cooled down at −10 K/min until room temperature, with the only purpose of relieving residual stresses. The next step was to apply the hot rolling process to the alloy. The sample initially measured, approximately, 1.5 cm of thickness when it was inserted into the furnace at 1203 K to start the hot rolling. Every pass on the hot rolling reduced the thickness by 0.5 mm, originating uniform and homogeneous samples of 2.5mm thickness. Auxiliary technical tools, such as XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), and EDS (Energy Dispersive X-Ray Spectroscopy), were used to analyze the microstructure of the samples before and after the hot rolling process. The XRD results show the formation of only a single α-HCP (Hexagonal Close Packed) phase for our samples, indicating that they are free of other phases that can damage the material. This result is consistent and coherent with both SEM and EDS analysis. The observed homogeneity of our samples is very good; proving that both techniques employed to obtain Zr1Nb as well as the hot rolling process was well succeeded. Therefore, the obtained alloy can be directly used in the pipes of nuclear combustible industries.Artigo IPEN-doc 23706 Measurements of residual stresses in aluminum wheels using the techniques of XRD, strain gages and FEA simulation - a comparison2016 - CIONE, FRANCISCO C.; SOUZA, ARMANDO; MARTINEZ, LUIZ; ROSSI, JESUALDO; BETINI, EVANDRO G.; ROLA, FABIO; COLOSIO, MARCO A.Studying the formation and distribution of residual stress fields will improve the wheel safety operational criteria among other gains. Many engineering specifications, manufacturing procedures, inspection and quality control have begun to require that the residual stress of a particular component to be evaluated. It is known that these residual stress fields could be added to the effects of a system load (tare weight plus occupation of vehicle, traction, braking and torque combined). The mathematical tools for modeling and simulations using finite elements had evolved following the increasing computing power and hardware cost reduction. On the other hand, the experimental testing, offers specific physical component behavior and with the use of statistical tools, it is possible to predict the real behavior of the component when in operation. The experiments undertaken used the X-ray diffraction technique and the drilling method with rosette type strain gages. The experimental results were convergent with similarity to those obtained using FEA simulation over critical region for global and superficial in the principal stresses mode. The relevance of the present study and research on residual stresses meets safety improvements in car’s wheel industry.Artigo IPEN-doc 18681 Residual stresses measurements using strain gages - aluminium wheels2012 - CIONE, F.C.; ROSSI, J.L.; SOUZA, A.C.; DELIJAICOV, S.; COLOSIO, M.A.