Banca de DEFESA: MÚCIO DANTAS DE MEDEIROS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : MÚCIO DANTAS DE MEDEIROS
DATE: 30/12/2020
TIME: 09:00
LOCAL: Sala virtual (videoconferência)
TITLE:

Directional solidification and wear resistance of Zn-8% Al-x% Cu alloys

KEY WORDS:

solidification; Zn-Al-Cu alloys; thermal parameters; microstructure; hardness.

PAGES: 85
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUMMARY:

Zinc is one of the most non-ferrous metals produced after aluminum and copper, being the most used in functional and decorative applications. The main advance in the foundry industry for zinc-based alloys in recent years has been in the development of new zinc-aluminum alloys. However, Zn-Al alloys have a low lubrication level, low ductility at room temperature and reduced mechanical strength  at high temperature. In this sense, this work aims to study the effects of Cu additions on the solidification thermal parameters such as cooling and growth rates (Ṫ_L/V_L-liquidus isotherm and Ṫ_E/V_E-eutectic front), microstructure (dendritic and eutectic arrangements), hardness and wear resistance of a hypereutectic Zn-8wt.%Al alloy. Techniques such as X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Optical Microscopy (OM) and Scanning Electronics (SEM) were used to characterize the as-cast samples. The results showed that Zn-Al-Cu alloys are formed by an eutectic matrix [(Zn)+(Al+Zn)] with lamellar and fibrous morphology also containing τ'-Al₄Cu₃Zn intermetallic particles and Al-rich pro-eutectic dendrites (Al'), with alternating lamellae of Al and Zn, from the eutectoid transformation [(Al')↔(Al)+ (Zn)]. The addition of 0.8wt.% Cu did not change the secondary dendritic arm spacing (λ₂), while a 1.3wt.% Cu content generated a slight dendritic refinement. The Cu additions have coarsen the fibrous (λ_EF) and lamellar (λ_EL) eutectic of the binary Zn-8wt.%Al alloy, with exception of the Zn-8wt.% Al-1.3wt.% Cu alloy, which showed a refinement of the fibrous eutectic for V_E> 0.30 mm/s. Increase in hardness has been observed for both Cu-modified alloys due to the solid-solution strengthening mechanism and presence of the τ'-Al₄Cu₃Zn intermetallics. An expressive increase of about 73.4% has been observed due to the addition of 1.3% Cu, which is also related to lower eutectic fibrous spacings. The Zn-8wt.%Al-0.8wt.% Cu alloy showed higher wear resistance associated with a lower fraction of τ’-Al₄Cu₃Zn.

BANKING MEMBERS:
Presidente - 2345599 - BISMARCK LUIZ SILVA
Externo ao Programa - 1652765 - MAURÍCIO MHIRDAUI PERES
Externo à Instituição - WASHINGTON LUIS REIS SANTOS - UNESP