DEENP - Artigos publicados em periódicos
URI permanente para esta coleçãohttp://www.hml.repositorio.ufop.br/handle/123456789/557
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Item Microstructural and segregation efects afecting the corrosion behavior of a high‐temperature Bi‐Ag solder alloy in dilute chloride solution.(2021) Azeredo, Rudimylla Septimio; Cruz, Clarissa Barros da; Silva, Bismarck Luiz; Garcia, Amauri; Spinelli, José Eduardo; Cheung, NoéIn electronic devices the solder joint is exposed not only to the air but also to moistures and other corrosive media such as chlorine and sulfur compounds. Bi–Ag alloys meet the melting temperature requirement to be classifed as high-temperature solders, therefore, knowledge of corrosion behavior is important for a long-term reliability of Bi–Ag solder connections. However, corrosion studies of Bi–Ag alloys are quite restricted in the literature. In this study, the role of the representative length scale of the microstructure as well as of the efects of Ag segregation on the resulting corrosion behavior of Bi–4 wt% Ag alloy samples are investigated. Cyclic potentiodynamic polarization and electrochemical impedance spectroscopy measurements were performed, and an equivalent circuit was also proposed to simulate the electrochemical corrosion behavior. All the used techniques indicated a tendency of better corrosion resistance associated with the sample having coarser microstructure and less Ag content.Item Corrosion behavior of an AleSneZn alloy : effects of solidification microstructure characteristics.(2021) Barros, André dos Santos; Cruz, Clarissa Barros da; Garcia, Amauri; Cheung, NoéDue to its strong influence on service life of manufactured parts, corrosion resistance is an important factor to consider when designing Al alloys for engineering applications. With this in mind, the present study focuses on understanding the role of microstructure features in the corrosion behavior of an Al-10wt.%Sn-5wt.%Zn alloy. Samples with different microstructural length scales were subjected to corrosion tests, which were performed using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. An equivalent circuit analysis was also carried out. The results revealed a relatively high electrochemical activity of the studied alloy. Furthermore, coarsening in microstructure showed a slight tendency towards improvements in the corrosion resistance, that is, coarser microstructures composed by Al-rich dendrites surrounded by SneZn constituent particles were comparatively less prone to corrosion degradation than finer ones. Finally, the proposed equivalent circuit model is shown to have good agreement with the experimental EIS measurements.Item Effect of microstructure features on the corrosion behavior of the Sn‐2.1 wt%Mg solder alloy.(2020) Cruz, Clarissa Barros da; Lima, Thiago Soares; Soares, Marco César Prado; Feitosa, Emmanuelle Sá Freitas; Fujiwara, Eric; Garcia, Amauri; Cheung, NoéThe Sn–Mg eutectic alloy is a potential replacement for the traditional Sn-38.1 wt%Pb solder alloy, since lead has been banned because of its risk to human health and the environment. However, studies in the literature related to the Sn-2.1 wt%Mg alloy are restricted to mechanical, electrical and thermal properties. Therefore, this study aims to evaluate the corrosion behavior of this alloy, as a function of the microstructural arrangement obtained from directional solidifcation performed in a transient heat extraction regime. The thermal solidifcation parameters (solidifcation growth rate and cooling rate) were determined along the length of the casting for correlations with microstructural features. The resulting microstructure was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray difraction. Subsequently, the electrochemical impedance spectroscopy, linear polarization, equivalent circuit and evolution of hydrogen release analyzes were performed to evaluate the corrosion behavior of the samples in a 0.5 M NaCl solution at 25 °C. Interphase spacing and Mg2Sn fraction were found to infuence the corrosion behavior, showing higher corrosion resistance for a more refned microstructure.