Attempts to produce functional aluminium components directly using rapid prototyping techniques has relied upon sintering of the green body to high density. Although this is possible, maintaining dimensional accuracy of a large, uncompacted powder preform with a complex geometry is not achievable. Since dimensional accuracy is critically important, the inability to accurately produce large parts has prevented commercialisation of these sintering systems. In this paper, recent advances in the selective laser sintering of aluminium and the development of a new infiltrated aluminium prototyping and rapid manufacturing system are discussed that can be used to fabricate large, intricate parts. The powder system consisted of 6061 Al alloy powder mixed with 2wt% elemental Mg and 10 vol% (4wt%) nylon powder. Parts were sintered using a laser power of 28W, part bed and feed temperatures of 120 C degree and 65 C degree, respectively and a layer thickness of 0.1 mm. The parts were then laid in a crucible and a block of infiltrant of equal mass was placed at one end and the assembly covered in either alumina or an alumina-1wt% Mg mixture. Subsequent sintering and infiltration occurred in a sealed horizontal tube furnace, using high purity nitrogen with a dew point of 70 C degree. Parts were either heated directly to the infiltration temperature of 570 C degree or held at 540 C degree for times up to 10 hours and then heated to 570 C degree. The ternary Al-13.8Si-4.7Mg eutectic, which has a melting point of 557 C degree, was used as the infiltrant. Parts for metallographic investigation were mounted in epoxy and polished using standard techniques. Samples were left unetched and Pt coated. Electron microscopy was undertaken using a Philips XL30 microscope with an EDAX Energy Dispersive Spectroscopy (EDS) analyser.
Selective laser sintering of aluminium
2003
8 Seiten, 8 Bilder, 1 Tabelle, 8 Quellen
Conference paper
English
Rapid-Prototyping , endabmessungsnahe Fertigung , selektives Laserstrahlsintern , Aluminium , Magnesium , Nylon , Sintern , Schichtdicke , Tiegel , Tränkung (Infiltration) , Taupunkt , ternäres System , Metallographieverfahren , EDS (energiedispersive Spektrometrie) , Dichte (Anzahl pro Volumen) , Grünling
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