JOAO VICTOR DE SOUSA ARAUJO
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Artigo IPEN-doc 27178 Galvanic and asymmetry effects on the local electrochemical behavior of the 2098-T351 alloy welded by friction stir welding2020 - MILAGRE, MARIANA X.; DONATUS, UYIME; MOGILI, NAGA V.; SILVA, REJANE M.P.; VIVEIROS, BARBARA V.G. de; PEREIRA, VICTOR F.; ANTUNES, RENATO A.; MACHADO, CARULINE S.C.; ARAUJO, JOAO V.S.; COSTA, ISOLDAScanning electrochemical microscopy (SECM) and scanning vibrating electrode technique (SVET) were used to investigate the electrochemical behaviour of the top surface of the 2098-T351 alloy welded by friction stir welding (FSW). The SVET technique was efficient in identifying the cathodic and anodic weld regions. The welding joint (WJ), which comprises the thermomechanically affected zone (TMAZ) and the stir zone (SZ), was cathodic relative to the heated affected zone (HAZ) and the base metal (BM). The reactivities of the welding joint at the advancing side (AS) and the retreating side (RS) were analyzed and compared using SECM technique in the competition mode by monitoring the dissolved oxygen as a redox mediator in 0.005 mol L−1 NaCl solution. The RS was more electrochemically active than the AS, and these results were correlated with the microstructural features of the welded alloy.Artigo IPEN-doc 25763 Effect of unequal levels of deformation and fragmentation on the electrochemical response of friction stir welded AA2024-T3 alloy2019 - QUEIROZ, FERNANDA M.; DONATUS, UYIME; RAMIREZ, OSCAR M.P.; ARAUJO, JOAO V. de S.; VIVEIROS, BARBARA V.G. de; LAMAKA, SVIATLANA; ZHELUDKEVICH, MIKHAIL; MASOUMI, MOHAMMAD; VIVIER, VINCENT; COSTA, ISOLDA; MELO, HERCILIO G. deThe effect of unequal levels of deformation and fragmentation on the electrochemical response of friction stir welded AA2024-T3 has been investigated using electron backscatter diffraction, scanning electron microscopy, global and localized electrochemical techniques. The friction stir welding process introduced unequal distribution and fragmentation of coarse intermetallic particles, such that more clusters of these particles were present in the thermomechanically affected zone of the weld. This resulted in a higher susceptibility to severe localized corrosion in this region when compared with the others. Results from electrochemical measurements using a microcell could not be clearly correlated with the corrosion behaviour because no significant differences were observed using these techniques. On the other hand, LEIS and SVET results were in agreement and correlated with the corrosion evolution at the surfaces of the tested samples.Artigo IPEN-doc 24705 On the severe localized corrosion susceptibility of the AA2198-T851 alloy2018 - ARAUJO, JOAO V. de S.; DONATUS, UYIME; QUEIROZ, FERNANDA M.; TERADA, MAYSA; MILAGRE, MARIANA X.; ALENCAR, MAICON C. de; COSTA, ISOLDAThe time dependent susceptibility of AA2198-T851 Al-Cu-Li alloy to severe localized corrosion in 0.01 mol L-1 NaCl solution has been investigated by immersion and SVET tests. The results reveal that the propagation of severe localized corrosion, in the alloy, is crystallographic and it is associated with the slip bands in the individual grains of the alloy. The slip bands caused uneven precipitation of the active T1 particles. Also, oscillations in SVET current density values associated with deposition and detachment of corrosion products were observed. Furthermore, the intensity of corrosion activities increased over time for open or partially covered pits.