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Master's Dissertation
DOI
https://doi.org/10.11606/D.97.2011.tde-22082013-170741
Document
Author
Full name
Francisco Henrique Cappi de Freitas
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Lorena, 2011
Supervisor
Committee
Nunes, Carlos Angelo (President)
Faria, Maria Ismenia Sodero Toledo
Machado, Antonio Jefferson da Silva
Title in Portuguese
Avaliação das relações de fases do sistema ternário Ni-Nb-Ta na região rica em Ni
Keywords in Portuguese
Diagrama de fases
Sistema Ni-Nb
Sistema Ni-Nb-Ta
Sistema Ni-Ta
Abstract in Portuguese
O presente trabalho está relacionado a estudos de superligas à base de Ni, cujas microestruturas multifásicas apresentam propriedades satisfatórias para aplicações em altas temperaturas. O Nb e o Ta são componentes importantes nesta classe de materiais, estando normalmente associados às fases endurecedoras ?' e ''. Desta forma, a determinação das relações de fases no sistema Ni-Nb-Ta na região rica em Ni corresponde a uma importante contribuição para a literatura referente, especialmente para os trabalhos ligados à construção de base de dados termodinâmicos. Assim, foi definido como objetivo principal a proposição das relações de fases na região rica em Ni do sistema Ni-Nb-Ta para a temperatura de 1050oC. As ligas foram obtidas por fusão a arco e tradas termicamente a 1050ºC por no mínimo 120 h. Amostras no estado bruto de fusão e tratadas termicamente foram caracterizadas microestruturalmente (MEV e DRX) e por microanálise química (EDS). Na região de estudo, observou-se as fases Niss, Ni8Ta, Ni3(Nb,Ta), Ni2(Nb,Ta), e ? (NiTa; Ni6Nb7), sem a presença de qualquer fase ternária. Observou-se uma solubilidade completa de Nb e Ta nas fases Ni3(Nb,Ta) e ?. A fase Ni2Ta apresentou uma solubilidade de Nb próxima de 13% at. Não foi possível determinar a região de solubilidade de Nb na fase Ni8Ta.
Title in English
Evaluation of phases relationships of the ternary system Ni-Nb-Ta at Ni-rich region
Keywords in English
Ni-Nb System
Ni-Nb-Ta System
Ni-Ta System
Phase diagram
Abstract in English
This work is related to studies of Ni-based superalloys, which multiphase microstructures have satisfactory properties for high temperature applications. The Nb and Ta are important components in this class of materials and is typically associated with the hardening phases ? ' and .'' Thus, the determination of phase relationships in the system Ni-Nb-Ta in the Ni-rich region represents an important contribution to the literature, especially for determination of related thermodynamic data. Thus, the main objective of this work was to propose the phase relationships in the Ni-rich region of the system Ni-Nb-Ta at 1050oC. The alloys were obtained by arc melting and heat-treated at 1050 º C for at least 120 h. Samples in the a-scast and heat treated states were characterized via (SEM and XRD) and chemical microanalysis (EDS). In the region of study, the observed phases were Niss, Ni8Ta, Ni3(Nb, Ta), Ni2(Nb,Ta), and ? (NiTa; Ni6Nb7) without the presence of any ternary phase. There was a complete solubility of Nb and Ta in the Ni3(Nb,Ta) and ? phases. The Ni2Ta showed a solubility of Nb close to 13% at. It was not possible to determine the region of solubility of Nb in the Ni8Ta phase.
 
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Publishing Date
2013-08-22
 
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