MARIANA XAVIER MILAGRE

MARIANA XAVIER MILAGRE

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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.
The effect of FSW on microstructure and intergranular corrosion of the AA2198- T8 alloy
2018 - MACHADO, C.S.C.; DONATUS, U.; ARAUJO, J.V.S.; KLUMPP, R.E.; MILAGRE, M.X.; GIORJAO, R.A.R.; MOGILI, N.V.V.; COSTA, I.
In this investigation, the intergranular corrosion (IGC) resistance of the AA2198-T8 alloy welded by friction stir welding (FSW) was investigated by ASTM G110-97 test. The different zones resulting from FSW showed distinct resistances to intergranular attack depending on the heating and/or mechanical effects produced by welding. The base metal (BM) was the most susceptible to IGC whereas the thermomechanically affected zone (TMAZ) and the stir zone (SZ), presented the highest resistances to IGC comparatively to the other zones. The results of IGC tests were correlated with those of thermal simulation, microhardness measurements, transmission electron microscopy (TEM) and optical microscopy (OM). The dissimilarities in corrosion resistance of the various zones were associated to differences in hardening phase quantities between the various zones. In the BM and HAZ, T1 phase, the main hardening phase, was found at grain boundaries and it resulted in IGC susceptibility. The slight IGC observed in the SZ and TMAZ was not associated with T1 phase which was rarely found but to another precipitate (T2 phase) which was found preferentially located at the grain boundaries in these zones.
Efeito dos tratamentos termomecânicos T8 e T851 na susceptibilidade a exfoliação e corrosão intergranular da liga AA2198
2018 - ARAUJO, J.V.S.; MACHADO, C.S.C.; MILAGRE, M.X.; COSTA, I.; FERREIRA, R.O.; VIVEIROS, B.G. de
As ligas Al-Cu-Li são ligas avançadas de grande interesse para a indústria aeronáutica devido à baixa densidade e alta resistência mecânica destas. Apesar destas vantages, estas apresentam susceptibilidade a diferentes tipos de corrosão. Além disso, os tratamentos termomecânicos aos quais são submetidas durante o processo de fabricação, afetam a microestrutura destas ligas bem como a resistência à corrosão destas. Existem alguns trabalhos publicados sobre a resistência à corrosão destas ligas, porém nestes trabalhos não se faz um comparação entre os efeitos dos diferentes tratamentos termomecânicos. Neste estudo foi investigado os efeitos dos tratamentos termomecânicos T8 e T851 na susceptibilidade à corrosão por exfoliação e corrosão intergranular (IGC) da liga AA2198, segundo as normas ASTM G34 e ASTM G110, respectivamente. Os resultados mostraram significativas diferenças na microestrutura das duas condições, com liga submetida ao tratamento T8 apresentando grãos alongados enquanto a exposta ao tratamento T851, grãos equaxiais. Ambas as ligas apresentaram suscetibilidade a exfoliação. Entreanto, enquanto a liga T8 apresentou susceptibilidade à corrosão intergranular e intragranular, a liga T851 não foi suscetível à corrosão intergranular, apresentando ataque de corrosão dentro dos grãos, ou seja, corrosão intragranular.
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.