Avaliação das ligas Al-5%Cu e Al-4%Cu-1%Ni tratadas por refusão à laser para aplicação em manufatura aditiva
The processing of metals and alloys via Additive Manufacturing (AM) has received special attention in recent years due to the possibility of obtaining parts with complex geometries, quickly and with minimal waste of raw material. Aluminum-based alloys are potential candidates for these processes,...
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| Formato: | Dissertação |
| 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/123456789/49477 |
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| Resumo: | The processing of metals and alloys via Additive Manufacturing (AM) has received
special attention in recent years due to the possibility of obtaining parts with complex
geometries, quickly and with minimal waste of raw material. Aluminum-based alloys
are potential candidates for these processes, however, currently there are few
candidates Al-based alloys for use in AM, such as Al-12wt.%Si and Al-10wt.%Si-xMg
system. This occurs because such alloys are susceptible to the formation of pores,
cracks, distortions and roughness, which impair high performance applications. The
addition of Ni in Al-Cu alloys system makes it possible to improve the mechanical
properties at high temperatures and favors the reduction of the solidification interval,
which results in a decrease in the amount of hot cracks and porosity in the final
material. Given the context, the present research investigates the microstructural
changes and the hardness of Al-5wt.%Cu and Al-4wt.%Cu-1wt.%Ni alloys processed
by rapid solidification (centrifugation) and treated Laser surface remelting (LSR), in
order to reproduce similar AM process conditions (high cooling rates 103
-108 K/s). In
order to understand the effect of Ni on the solidification interval, fraction of
intermetallics and on temperatures and phase transformations, simulations and
thermodynamic calculations were carried out by Thermo-calc software.
Characterization techniques such as optical microscopy (OM), scanning electron
microscopy (SEM) and X-ray diffraction (XRD) were used, in addition to thermal
analysis by Differential Scanning Calorimetry (DSC) and Vickers microhardness. The
simulations revealed a reduction of the solidification interval of approximately 22% in
the Al-4.0wt.%Cu-1.0wt.%Ni alloy, and consequently, a decrease in the porosity of the
Laser remelted pools. The microstructure of the rapidly solidified samples is
characterized by a α-Al dendritic matrix, surrounded by a eutectic mixture α-Al, Al2Cu
and Al7Cu4Ni. In the remelted pools, there was a transition from epitaxial (pool base)
to equiaxed (pool center) growth with a significant microstructural refinement around
92% (from λ1=7.63 - 7.41 µm to λ1=0.681 - 0.609µm), which favored an increase of
about 82-90% (Al-5wt.%Cu: from 58.4 HV to 106.9 HV / Al-4wt.%Cu-1wt.%Ni: from
60.5 HV to 117 HV) of the microhardness in the microstructures Laser treated. |
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