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Asavavisithchai S.,Innovative Metals Research Unit | Jareankieathbovorn N.,Innovative Metals Research Unit | Srichaiyaperk A.,Innovative Metals Research Unit
Advanced Materials Research | Year: 2014

Open-cell Al foam has outstanding properties which are suitable for functional applications. However, a major drawback for widespread employment of Al foam is its high relative cost which can be several times higher than conventional metals. To reduce the cost, a recycled material waste is constructively used instead of expensive base metal. The present study aims to fabricate economical open-cell Al foams using AC8A alloy scrap from lathe machines. The Al foams were fabricated through pressure infiltration casting process at which the cellular pattern was made from commercial reticulated open-cell polyurethane foams with the pore size of 12 ppi. The compressive strength and microhardness of scrap-recycled Al foams are higher than those of pure Al foam. The increase in foam mechanical properties resulted from the change in foam microstructure as the formation of Si hard phase in Al matrix. The strength and microhardness of the foams increase with increasing scrap contents. © (2014) Trans Tech Publications, Switzerland. Source

Asavavisithchai S.,Innovative Metals Research Unit | Preuksarattanawut T.,Innovative Metals Research Unit | Nisaratanaporn E.,Innovative Metals Research Unit
Materialpruefung/Materials Testing | Year: 2014

Hollow silver particles with three different shapes, i. e., spherical, cylindrical, and octahedral, were used as raw material to produce open-cell silver foams. The shape difference of the particles resulted from the reduction of different shaped silver sulfates. Fabrication of silver foams was carried out using SDP process with disaccharide particles as space holder. The resultant silver foams show high porosity with distinctive pore microstructures. The examination of pore structure by SEM shows that there are three levels of porosities which are unique for each type of foam. The foams, using spherical and cylindrical silver particles, have a larger surface area and a higher density than the foam with the silver particle of octahedral shape. A control of pore architecture can be performed by tailoring material and process parameters. The difference in pore architecture resulted in a different compressive behaviour of the foams. As expected, the foam, using octahedral silver particles, has lower compressive strength than the others, mostly due to lower foam density. © Carl Hanser Verlag GmbH & Co KG. Source

Hirunyagird J.,Innovative Metals Research Unit | Chianpairot A.,Innovative Metals Research Unit | Nisaratanaporn E.,Innovative Metals Research Unit | Lothongkum G.,Innovative Metals Research Unit
Materialpruefung/Materials Testing | Year: 2014

This work studies the effects of Zn/Cu ratio and silicon on the improvement of mechanical properties, tarnish and corrosion resistance of 940 silver alloys. The silver alloys to be investigated are divided into 2 groups. The group 1 alloys are Ag-Cu-Zn alloys. The group 2 alloys are Ag-Cu-Zn-0.02Si alloys. The microstructures of all alloys to be tested look similar and consist of a Ag-rich matrix (a phase) and Cu-rich eutec-tic structure (α + β phase). The proportion of eutectic structure decreases by increasing Zn/Cu ratio. Increasing Zn/Cu ratio significantly decreases hardness, ultimate tensile strength, but markedly increases elongation. Addition of 0.02wt.-%Si to Ag-Cu-Zn alloys has no effect on hardness and ultimate tensile strength, but decreases elongation. The tarnish and corrosion resistance of Ag-Cu-Zn alloys in 1 % NaCl solution at 298 K significantly increases with increasing Zn/Cu ratio. Addition of silicon also improves tarnish resistance. © Carl Hanser Verlag GmbH & Co. KG. Source

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