Título: | QUANTIFICATION OF AUSTENITE-MARTENSITE IN LOW ALLOY STEEL BY IMAGE ANALYSIS | ||||||||||||
Autor: |
JULIO DAMIAN SUNI MAMANI |
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Colaborador(es): |
SIDNEI PACIORNIK - Orientador IVANI DE SOUZA BOTT - Coorientador |
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Catalogação: | 05/MAI/2014 | Língua(s): | PORTUGUESE - BRAZIL |
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Tipo: | TEXT | Subtipo: | THESIS | ||||||||||
Notas: |
[pt] Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio. [en] All data contained in the documents are the sole responsibility of the authors. The data used in the descriptions of the documents are in conformity with the systems of the administration of PUC-Rio. |
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Referência(s): |
[pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=22902&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=22902&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.22902 | ||||||||||||
Resumo: | |||||||||||||
This dissertation proposed the development of a quantification method, by
microscopy, of the microconstituent Martensite-Austenite (MA) in a High
Strength Low Alloy (HSLA) steel of the API5LX80 class. Images were obtained
by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), in
secondary electron (SE) and backscattered electron (BSE) modes. Digital Image
Processing and Analysis (IA) was employed to process and quantify the acquired
images and compare the results of the two types of microscopy. The main
challenge was to discriminate the MA amidst a complex multiphase
microstructure with varying fractions of ferrite, bainite and MA itself. To reveal
the MA different chemical and electrolytic etching sequences were tested. The
results showed that a mixed combination with an extra step of modified LePera
etchant issued the best contrast for both OM and BSE mode SEM. SEM images in
SE mode showed edge problems due to the location of the electron detector, what
prevented the correct discrimination of MA regions. The accelerating voltage in
the BSE mode was reduced to 5 kV which in turn decreased beam penetration and
increase contrast due to the thin MA layer. These images were filtered to reduce
noise and segmented by a simple threshold to quantify MA. In the color OM
images MA was segmented by thresholds in the RGB or HSB color spaces and
subsequently quantified. Employing Co-Site Microscopy images of identical
fields acquired by OM and SEM, a direct comparison of the techniques was
allowed. It was show that, for the same magnification, optical microscopy tends to
underestimate the MA fraction when compared to electron microscopy in BSE
mode.
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