Estudo sobre a influência do tempo de polimento por imersão em sílica coloidal nas análises via EBSD de um aço TRIP laminado a frio
Steels assisted by the TRIP effect have stood out due to their multiphase microstructure, which offers a combination of properties that enables the development of automotive parts with excellent mechanical properties. This improvement in properties occurs through the transformation of austenite reta...
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| Formato: | bachelorThesis |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/40383 |
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| Resumo: | Steels assisted by the TRIP effect have stood out due to their multiphase microstructure, which offers a combination of properties that enables the development of automotive parts with excellent mechanical properties. This improvement in properties occurs through the transformation of austenite retained in martensite during plastic deformation. Therefore, the fraction of austenite retained in the steel directly influences its properties, making the microstructural analysis of the steel become one of the most important steps for the development of automotive steels and one of the techniques widely used for the quantification of phases is the EBSD (Electron Backscattering Diffraction). This technique requires well-polished samples for an effective removal of the hardened layer during the preparation steps, thus avoiding obtaining false values in the quantification of the phases. A technique that is efficient in removing the hardened layer is fine polishing on colloidal silica. Therefore, this work aims to study the influence of the polishing time by immersion in colloidal silica on the results of analyzes via EBSD of a cold-rolled TRIP steel. To carry out this work, a TRIP 780 steel was used, in which, after the initial sample preparation steps, polishing was performed on colloidal silica for different times, between 1 and 12 hours. Analyzes were performed via EBSD, in order to follow the evolution of the results obtained with the increase of the polishing time. The results obtained were represented by means of phase maps and crystallographic orientations and by the parameters IQ (Image Quality), KAM (Kernel Average Misorientation) and percentage of phases. Analyzing the behavior of the maps, the IQ and the phase quantification, an increase in the percentage of austenite and the average IQ is noted with the increase in the polishing time. The values obtained in the KAM show a decrease as the polishing time increases. With the T-Student test, it was possible to affirm with 95% of significance that the polishing time presents a significant difference in the mean values of IQ and KAM only up to 4 hours of polishing, so that for longer times there is no more influence on the results evaluated, indicating that this polishing time is sufficient to remove the superficial layers of the samples that have undergone transformations due to the metallographic preparation steps that preceded the final polishing in colloidal silica. |
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