Banca de QUALIFICAÇÃO: MARCELA BERGAMASCHI TERCINI
Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.STUDENT : MARCELA BERGAMASCHI TERCINI
DATE: 07/02/2023
TIME: 14:00
LOCAL: Bloco A
TITLE:
Corrosion study of Cu45Zr45Al10 metallic glasses and their composites in NaCl solution
PAGES: 75
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
SPECIALTY: Corrosão
SUMMARY:
Metallic Glasses (MG) are metallic alloys that have an amorphous structure. These materials exhibit unique properties, such as extensive elastic deformation, however shows a brittle fracture. Therefore, several studies are searching for the increase of the plastic deformation in MG. And a very efficient technique is adding a second phase, which can be ex-situ (addition of a material) or in-situ (precipitates). The material with a in-situ second phase is formed by an amorphous matrix embedded with crystals, that is named Metallic Glass Composite (MGC). About the corrosion resistance of MG and their composites, it is not well understood how the variation of the concentration and size of the crystals affects the corrosion resistance. Therefore, this work will study the correlation between the corrosion resistance with the size and concentration of crystals in metallic glasses and their composites. First, an alloy of Cu45Zr45Al10 with different concentrations of crystals was produced. The microstructure was analyzed with SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction). Afterwards, electrochemical impedance spectroscopy analyzes were made at 1, 24, 48, 72, 96 and 168 hours of immersion in a NaCl solution (0.1 M), followed by the polarization test, both analyzes were made in the Autolab M101 potentiostat /galvanostat. With the XRD and SEM analyses, the samples could be divided into 3 groups: 1) amorphous (MG), 2) composite with small crystals (MGC-P) and 3) composite with big crystals (MGC-G). The Nyquist diagram shows that the MGC-P group has the larger capacitive arc radius and the MGC-G group the smaller radius, meaning that the sample with small crystals has the greatest corrosion resistance, followed by the amorphous sample and by the sample with large crystals (worst corrosion resistance). This was confirmed by the polarization graph, that shows the CVM-P group has the smaller Ecorr and the CVM-G group has the bigger Ecorr. The MG has a higher corrosion resistance than the CVM-G, which is in agree with the literature, which reports that the MG have a higher corrosion resistance, because they do not have a localized corrosion at the interface of MG/crystal [1]. However, the literature also reports that in Zr-based alloys, the devitrification process can facilitate the formation of the passive film [2]. So, the CVM-P can exhibited better corrosive properties than MG. Then, the next steps of this work will be the characterization of the passive film formed in different times of immersion in NaCl solution with XPS (X-Ray Photoelectron Spectroscopy) and Raman spectroscopy in order to assess compositional differences, and with SEM, to examine the surface morphology of the different samples.
COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 1671292 - SYDNEY FERREIRA SANTOS
Membro Titular - Examinador(a) Interno ao Programa - 1282172 - ROBERTO GOMES DE AGUIAR VEIGA
Membro Titular - Examinador(a) Externo ao Programa - 1646041 - CARLOS TRIVENO RIOS
Membro Titular - Examinador(a) Externo ao Programa - 2604737 - EVERALDO CARLOS VENANCIO
Membro Suplente - Examinador(a) Interno ao Programa - 1760410 - JEVERSON TEODORO ARANTES JUNIOR
Membro Suplente - Examinador(a) Interno ao Programa - 1671394 - HUMBERTO NAOYUKI YOSHIMURA
Membro Suplente - Examinador(a) Interno ao Programa - 1734912 - ROOSEVELT DROPPA JUNIOR
Membro Suplente - Examinador(a) Interno ao Programa - 1545738 - MARCIA TSUYAMA ESCOTE