MARIANA XAVIER MILAGRE

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Autor: CARULINE DE SOUZA CARVALHO MACHADO × search.filters.applied.f.ispartof: Materials Characterization ×

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    Artigo IPEN-doc 27812
    How microstructure affects localized corrosion resistance of stir zone of the AA2198-T8 alloy after friction stir welding
    2021 - MACHADO, CARULINE de S.C.; DONATUS, UYIME; MILAGRE, MARIANA X.; ARAUJO, JOAO V. de S.; VIVEIROS, BARBARA V.G. de; KLUMPP, RAFAEL E.; PEREIRA, VICTOR F.; COSTA, ISOLDA
    In this study, the microstructure and corrosion resistance of the stir zone (SZ) of the AA2198-T8 Al-Cu-Li alloy welded by friction stir welding (FSW) were investigated by microscopy, immersion tests and electrochemical techniques such as measurements of open circuit potential variation with time, and scanning vibrating electrode technique (SVET) measurements. A low chloride-containing solution (0.005 mol L−1 NaCl) was employed in the corrosion studies and severe localized corrosion (SLC) was observed in the SZ related to intergranular attack. The results were compared to those of the non-affected areas by FSW, also known as base metal (BM). In the BM, SLC was found and the type of attack related to it was intragranular. In both zones, BM and SZ, SLC was due to precipitates of high electrochemical activity, specifically T1 (Al2CuLi) phase in the BM, whereas TB (Al7Cu4Li) / T2 (Al6CuLi3) in the SZ. Scanning vibrating electrode technique (SVET) analysis was very useful in the study of SLC in the AA2198-T8 alloy showing the development of high anodic current densities at the mouth of the SLC sites.
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    Artigo IPEN-doc 24759
    On the microstructure characterization of the AA2098-T351 alloy welded by FSW
    2018 - MILAGRE, MARIANA X.; MOGILI, NAGA V.; DONATUS, UYIME; GIORJAO, RAFAEL A.R.; TERADA, MAYSA; ARAUJO, JOAO V.S.; MACHADO, CARULINE S.C.; COSTA, ISOLDA
    The complex structure of the AA2098-T351 alloy welded by friction stir welding (FSW) was investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and microhardness measurements. Thermal modelling process of the FSW process was carried out by soldering thermocouples at distances of 6, 9 and 12 mm from the weld centerline, and thermocouple measurements were used as input data into the model. Finite element software COMSOL v5.2 was used for data analysis. The prevailing phases in the base metal (BM) are T1 (Al2CuLi) theta' (Al2Cu), delta'/beta'(Al-3(Li,Zr)) and Omega (Al2Cu). In the heat affected zone (HAZ), either in the retreating or advancing sides, theta' phase was not identified. In the thermomechanical affected zone (TMAZ), T1, delta'/beta', GP zones phase were detected in the retreating side, whereas T1 and Guinier-Preston (GP) zones were not observed in the advancing side. This result supports the asymmetric behavior observed in the microhardness profile of the weld. In the stir zone (SZ), GP zones, T1, delta'/beta' (Al-3(Li,Zr)) and Omega were identified.