Estudo de duas pseudoligas de Nb-Cu obtidas pela rota da metalurgia do pó
The Nb-Cu pseudoalloys present themselves as potential substitutes for the alloys from a well known system and already commercially applied, as the W-Cu alloys, used in applications such as heat sinks, electrical contacts and coils for the generation of high magnetic fields. Because it is an immi...
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| Formato: | doctoralThesis |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/20091 |
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| Resumo: | The Nb-Cu pseudoalloys present themselves as potential substitutes for the alloys from a well
known system and already commercially applied, as the W-Cu alloys, used in applications
such as heat sinks, electrical contacts and coils for the generation of high magnetic fields.
Because it is an immiscible system, where there is mutual insolubility and low wettability of
the liquid Cu on the Nb surface, the processing route used in this work was the Powder
Metallurgy. Two Nb alloys were used, with additions of 10% and 20% in weight of Cu, and
times of 20, 30 and 40 hours for the high energy milling of the starting powders. The milling
evolution of the powders is presented through the characterization techniques, such as the
LASER diffraction for particle size, XRD, SEM, EDS, DSC, dilatometry, TEM and chemical
analysis. After the milling, portions of the loads were submitted to the annealing heat
treatment. The process used for the samples consolidation was the hot pressing, which has
been applied both on some milled powders samples, as on the annealed powders. Subsequent
heat treatments were performed in the samples at temperatures of 1000ºC (solid phase) and
1100ºC (in the Cu liquid phase). All sets of consolidated samples, and also the two sets of the
heat treated, were analyzed by XRD, SEM, EDS, density and Vickers microhardness.
Moreover, other Nb powder samples with 10% and 20% in weight of Cu obtained by simple
mechanical mixing, were consolidated, thermally treated and characterized with the same
techniques applied to the others, and the results were compared among themselves. Despite
the difficulty of consolidation and densification of the two pseudoalloys of the Nb-Cu system
of this study, on the route that passes through the HEM, samples were obtained with densities
around 90% of the theoretical density. And, on the processing route of which were only
mixed, the values reached up to 97%. Therefore, in this work are also emphasized the
processes that made possible these results. |
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