MARIANA XAVIER MILAGRE

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20202
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Agência de fomento: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) × Assunto: lithium alloys ×

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    Artigo IPEN-doc 27430
    Exfoliation and intergranular corrosion resistance of the 2198 Al–Cu–Li alloy with different thermomechanical treatments
    2020 - ARAUJO, JOAO V. de S.; MILAGRE, MARIANA X.; FERREIRA, RAPHAEL O.; MACHADO, CARULINE de S.C.; BUGARIN, ALINE de F.S.; MACHADO, IZABEL F.; COSTA, ISOLDA
    In this study, the resistance to exfoliation and intergranular corrosion (IGC) of the 2198 Al–Cu–Li alloy submitted to different thermomechanical treatments (T3, T8, and T851) was investigated. The tests were carried out following the standard practices, ASTM G34‐18 and ASTM G110‐15, respectively. All the tested alloys showed susceptibility to exfoliation and some alloys showed susceptibility to IGC, but the artificially aged alloys presented a higher tendency to exfoliation. The extensive hydrogen evolution reaction (HER) was observed on the surfaces of artificially aged alloys when immersed in the EXCO solution. The HER resulted in an increase in solution pH with the time of immersion. Also, the weight losses related to the artificially aged alloys were higher than that of the naturally aged ones. The T8 treatment was the only condition that resulted in susceptibility to both, intergranular and transgranular corrosion, whereas the T851 treatment did not show IGC susceptibility, only transgranular corrosion. Finally, the 2198‐T3 condition showed the highest corrosion resistance among the thermomechanical treatments tested. The results of the 2198 alloy subjected to various treatments were compared with that of the 2024‐T3 alloy. This last alloy showed higher resistance to exfoliation and IGC as compared with the 2198 alloy.
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    Artigo IPEN-doc 27418
    Microstructural characteristics of the Al alloys
    2020 - ARAUJO, JOAO V. de S.; MILAGRE, MARIANA X.; FERREIRA, RAPHAEL O.; MACHADO, CARULINE de S.C.; ABREU, CAIO P. de; COSTA, ISOLDA
    Microstructure characteristics of two high-strength aluminum alloys, the 2024-T3 Al–Cu–Mg, and the new generation Al–Cu–Li alloy 2198, in the T8 and T851 tempers, were investigated in this study. For this purpose, microstructural and statistical analyses were carried out. The results showed equiaxed grains for the 2024-T3 and 2198-T851 alloys, whereas, elongated grains for the 2198-T8. Besides, the 2198-T851 alloy displayed slip bands in the grains due to the stretching stage, “51”. The 2024-T3 alloy showed at least two types of constituent particles, Al–Cu–Mg and Al–Cu–Mn–Fe–(Si); whereas Al–Cu–Li alloys showed only one type, Al–Cu–Fe, in their composition. Statistical analyses showed that the percentage of area covered by constituent particles was larger in the 2024-T3 alloy compared to the 2198 in both tempers, T8 and T851. On the other hand, the Al–Cu–Li alloys showed higher microhardness values relatively to the Al–Cu one. The differences among the nanometric phases present in Al–Cu and Al–Cu–Li alloys were analyzed by transmission electron microscopy. All the results were related to the different chemical composition and industrial thermomechanical processing of each alloy.