JOAO VICTOR DE SOUSA ARAUJO

JOAO VICTOR DE SOUSA ARAUJO

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Intergranular corrosion susceptibility of Al-Cu-Li alloys
2017 - MILAGRE, MARIANA X.; MACHADO, CARULINE S.C.; ARAUJO, JOAO V.; ASTARITA, ANTONELLO; PEBERE, NADINE; VIVIER, VINCENT; COSTA, ISOLDA
In the present study, the intergranular corrosion (IGC) susceptibility of commercial Al-Cu-Li alloys of the third generation (AA2098-T351, AA2198-T3 and AA2198-T851) was compared with that of the AA2024-T3 alloy according to ASTM G110 test. In addition, anodic and cathodic polarization curves were carried out in the ASTM G110 test solution at room temperature. The cross-section of the samples after the ASTM G110 test was observed by scanning electron microscopy (SEM) to evaluate the extension of the corrosion attack. The susceptibility to intergranular attack of the tested alloys was ranked according to the attack by IGC and from the anodic and cathodic polarization curves. The results showed that the AA2024-T3 and the AA2198-T3 alloys presented higher susceptibility to intergranular corrosion comparatively to the other alloys tested (AA2098-T351 and AA2198-T851). The AA2098-T351 alloy was associated to the highest resistance to intergranular attack among the alloys evaluated. A correlation was seemingly established between the stress relief treatment of the alloy and its corresponding susceptibility to intergranular or intragranular corrosion.
Effects of chloride ion concentration on the corrosion behavior of the AA2198-T8 alloy
2019 - MACHADO, CARULINE de S.C.; SILVA, REJANE M. da; ARAUJO, JOAO V. de S.; DONATUS, UYIME; MILAGRE, MARIANA X.; KLUMPP, RAFAEL E.; ROSSI, JESUALDO L.; COSTA, ISOLDA
In this work, the influence of chloride ions concentration on the corrosion behavior of the AA2198-T8 alloy was evaluated. Immersion test and electrochemical analyses were performed in sodium chloride solutions of three concentrations, 0.001 mol L-1, 0.005 mol L-1 and 0.01 mol L-1. The results showed that the AA2198-T8 alloy was susceptible to localized corrosion (LC) and to severe localized corrosion (SLC) in all conditions investigated. The electrochemical results obtained by open circuit potential measurements, cyclic voltammetry and potentiodynamic polarization curves were associated with the corroded microstructure of the alloy. Although electrochemical techniques allowed differentiating the corrosion resistance as a function of chloride concentration, the result was strongly influenced by the corroded/uncorroded area ratio related to the SLC.
Estudo da influência dos tratamentos termomecânicos T8 e T851 na microestrutura e no comportamento de corrosão da liga AA2198
2018 - ARAUJO, JOAO V. de S.; XAVIER, MARIANA M.; MACHADO, CARULINE S.C.; QUEIROZ, FERNANDA M.; COSTA, ISOLDA
Al-Cu-Li alloys present advantages in relation to conventional Al-Cu alloys in applications for aerospace industry due to their low density and good mechanical properties. The mechanical properties of these alloys depend on their microstructure and this is affected by the thermomechanical treatments to which the materials are submitted during their fabrication process. In the present study, the effects of T8 and T851 thermomechanical treatments on the corrosion resistance of the AA2198 alloy were compared. The main hardening precipitate in Al-Cu-Li alloys is the T1 phase, (Al2CuLi). The presence of this precipitate in the AA2198-T8 and T851 alloys was analyzed by transmission electron microscopy (TEM). The microstructure of both alloys was evaluated by Vickers micro hardness and differential scanning calorimetric (DSC) measurements and the results obtained were correlated. The results showed higher density of T1 phase for the T851 condition. Besides, microstructural characterization revealed elongated grains for the T8 condition and equiaxed grains for T851 condition. These results were related to the corrosion behavior of both alloys by immersion and gel visualization tests.
Exfoliation susceptibility of aluminum alloys joined by Friction Stir Welding (FSW)
2018 - MILAGRE, MARIANA X.; DONATUS, UYIME; MACHADO, CARULINE S.C.; ARAUJO, JOAO V. de S.; MOGILI, VISHNU; ASTARITA, ANTONELLO; COSTA, ISOLDA
In the present study, the exfoliation susceptibility of a commercial Al-Cu-Li alloy of the third generation, AA2098-T351, joined by FSW was investigated according to ASTM G34 standard practice and the results were compared with the results of the parent material. Susceptibility to exfoliation attack was classified by the depth of attack penetration. The cross-sections of the samples after test were observed by optical and scanning electron microscopy (SEM) to evaluate the penetration depth of corrosion attack. A comparison to conventional Al-Cu alloys (AA2024-T3/T351) was carried out and the results showed that the Al-Cu-Li alloy tested (AA2098-T351) was more susceptible to exfoliation. Besides, exfoliation susceptibility varied with each welded zone and the active zones remained active for long periods of time after removal from the test solution when the attack continuously propagated in the corrosion front.
Comparison of the corrosion resistance of AA2024 and AA2098 alloys in different solutions
2018 - MILAGRE, MARIANA X.; ARAUJO, JOAO V. de S.; GOMES, MAURILIO P.; DONATUS, UYIME; MACHADO, CARULINE S.C.; COSTA, ISOLDA
In this work the corrosion resistance of the AA2098-T351 and AA2024-T3 was evaluated and compared by electrochemical tests in 0.01 mol.L-1 of NaCl and 0.1 mol.L-1 of Na2SO4 with 0.001 mol.L-1 NaCl electrolytes. Monitoring of corrosion evolution in both alloys was carried out by electrochemical impedance spectroscopy (EIS) and polarization methods. The surface of the samples exposed to the test solutions was observed by microscopy after corrosion tests. The results showed different corrosion mechanisms in the two test solutions. In the sulfate containing electrolyte, the Al-Cu-Li alloy showed corrosion mechanism mainly associated with the micrometric particles at the surface, similarly to the AA2024-T3 alloy. However, in the chloride solution without sulfate, the AA2098-T351 alloy showed susceptibility to severe localized corrosion (SLC) besides the corrosion associated to the micrometric particles and the first type of corrosion was the main type of attack. The AA2024-T3 showed lower susceptibility to SLC than the AA2098- T351 alloy.
Avaliação da resistência a corrosão intergranular da liga AA 2198-T851 soldada pelo processo FSW
2016 - MACHADO, C.S.C.; MILAGRE, M.X.; ARAUJO, J.V.; TERADA, M.; COSTA, I.
In this work, the intergranular corrosion resistance of the Al-Cu-Li AA2198- 851 alloy, welded by friction stir welding (FSW) has been evaluated by ASTM G110-97 procedure. There was no susceptibility to intergranular corrosion of this alloy in the tested conditions.
Avaliação da resistência a corrosão intergranular da liga AA2198-T8
2016 - ARAUJO, J.V.; MACHADO, C.S.C.; MILAGRE, M.X.; QUEIROZ, F.M.; COSTA, I.
The intergranular corrosion is a form of corrosion which can result in loss of mechanical properties and might lead to rupture of the material. These properties are of fundamental importance for the materials used in aircraft for security reasons. It is important to characterize the intergranular corrosion resistance of materials used in aeronautical applications. This study investigated the intergranular corrosion resistance of the AA2198-T8 alloy that presents copper and lithium as the main alloying elements. The results showed that this alloys is susceptible to this form of corrosion.
Comparação do comportamento de corrosão da liga convencional AA2024-T351 e da liga Al-Li 2098-T351
2016 - MILAGRE, M.X.; ARAUJO, J.V.; QUEIROZ, F.M.; MACHADO, C.S.C.; COSTA, I.
In this work, the localized corrosion behavior of an Al-Li alloy (AA2098-T351) was compared with that of the AA2024-T351 conventional alloy by immersion test in 0.01 mol L-1 NaCl solution. The evolution of localized corrosion in both alloys was monitored by optical microscopy and scanning electron microscopy after several test periods from 2h to 24h. The results showed high susceptibility of the two alloys to pitting from the early hours of immersion. The corrosion mechanism in the two alloys, however, was different. Localized corrosion in the AA2024 alloy was associated with the microcells generation between micrometric precipitates and the matrix leading to superficial attack homogeneously distributed throughout the surface exposed to the corrosive environment. In the AA2098 alloy, however, a severe localized corrosion ascribed in the literature to the presence of phase T1 was also observed besides the localized corrosion type similar to that observed in the AA2024 alloy.