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Use of acoustic energy in sand casting of aluminium alloys

Puga, Hélder; Barbosa, J.; Oliveira, Joana

During the last years, some researchers have focused the development of ultrasonic microstructure refinement /modification techniques of die-casting aluminium alloys, to improve their properties. The developed techniques are highly efficient when applied to the die-casting process, but their capability with sand and ceramic moulding are unknown. Sand/ceramic aluminium castings are prone to coarse microstructure...


Factors affecting the metal recovery yield during induction melting of aluminiu...

Puga, Hélder; Barbosa, J.; Ribeiro, Carlos Silva

Machining operations of cast parts usually generate considerable amounts of waste in the form of chips (usually 3–5% of the casting weight). Traditionally, swarf is sold to scrapers and remelters, but this option is quite expensive because the selling price is roughly 30% of the acquisition price of the commercial 2nd melt raw material. For most aluminium foundries that incorporate machining operations in their...


Influence of indirect ultrasonic vibration on the microstructure and mechanical...

Puga, Hélder; Barbosa, J.; Costa, Sónia; Ribeiro, Carlos Silva; Pinto, A. M. P.; Prokic, Miodrag

The influence of high intensity ultrasound (US) propagating through a steel mold on the microstructure and mechanical properties of die-cast AlSi9Cu3, for different levels of electric power and at different distances to the waveguide/mold interface. The influence of those parameters on the morphology of -Al and eutectic Si and on the volume of porosity were investigated and characterized. The morphological ch...


Use of acoustic energy in the processing of molten aluminium alloys

Puga, Hélder; Barbosa, J.; Costa, Sónia; Ribeiro, Carlos Silva

During the last years aluminium alloys have been gaining increased acceptance as structural materials in the automotive and aeronautical industries, mainly due to their light weight, good formability and corrosion resistance. However, improvement of mechanical properties is a constant in research activities, either by the development of new alloys or by microstructure manipulation. This presentation focuses a ...


The influence of melt treatment process on the quality and permormance [i. é pe...

Puga, Hélder; Barbosa, J.; Silva, F. S.

The performance of a mechanical component is often limited by the intrinsic characteristics of the materials used or by weaknesses/limitations inherent to the manufacturing process. Despite their widespread use, the casting of aluminum alloys is not easy since they are prone to coarse and heterogeneous structures, usually dendritic. Moreover they are susceptible to hydrogen absorption during melting, requiring ...


The effect of Sc additions on the microstructure and age hardening behaviour of...

Costa, Sónia; Puga, Hélder; Barbosa, J.; Pinto, A. M. P.

The grain refinement effect and the ageing behaviour of Al–0.5 wt.% Sc, Al–0.7 wt.% Sc, and Al–1 wt.% Sc alloys are studied on the basis of optic microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) observations and hardness measurements. In Al–Sc alloys the higher grain refinement is observed for Sc contents greater than 0.5 wt.% accompanied by a notorious morphology modification, from ...


Evaluation of ultrasonic aluminium degassing by piezoelectric sensor

Puga, Hélder; Gabriel, Joaquim; Barbosa, J.; Seabra, Eurico; Ribeiro, Carlos Silva; Prokic, Miodrag

The purpose of this work was the development of a reliable technique to evaluate the intensity of acoustic cavitation during degassing of aluminium melts and to use it to select the optimum processing time for an envisaged degassing efficiency. A high sensitivity piezoelectric disk type device was used as a sensing feedback in water and liquid AlSi9Cu3 alloy. The signal acquisition and processing was carried ou...


Effect of melting pressure and superheating on chemical composition and contami...

Gomes, Fernando; Puga, Hélder; Barbosa, J.; Ribeiro, Carlos Silva

When melting reactive alloys, chemical composition and alloy homogeneity strongly depend on processing conditions, especially if melting is performed in ceramic crucibles. In this case, the nature of crucible materials, the melting stock composition and the melting parameters (atmosphere, pressure, superheating time and temperature) are critical processing variables. In this work, a Ti–48Al alloy was induction ...


Influence of ultrasonic melt treatment on microstructure and mechanical propert...

Puga, Hélder; Costa, Sónia; Barbosa, J.; S. Ribeiro, Carlos; Prokic, Miodrag

A novel MMM (Multi-frequency, Multimode, Modulated) ultrasonic (US) technology was used to refine the as cast microstructure and improve the mechanical properties of a AlSi9Cu3 alloy. Ultrasonic vibration was isothermally applied to the melt for 120 seconds at different temperatures slightly above the liquidus temperature of the alloy, using different electric power values, before pouring into a metallic mould....


The combined effect of melt stirring and ultrasonic agitation on the degassing ...

Puga, Hélder; Barbosa, J.; Teixeira, J. Carlos; Seabra, Eurico; Ribeiro, Carlos Silva; Prokic, Miodrag

The combined effect of high intensity ultrasound and melt stirring on the degassing of AlSi9Cu3 using simultaneously the novel MMM (Multi-frequency Multimode Modulated) ultrasonic technology to promote cavitation, and low frequency mechanical vibration to induce melt stirring, was studied. On a first stage single low frequency mechanical vibration experiments were carried out in water in order to visualize and ...


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Fundação para a Ciência e a Tecnologia Universidade do Minho   Governo Português Ministério da Educação e Ciência Programa Operacional da Sociedade do Conhecimento União Europeia