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Title: Thixoforming of Hypereutectic Al/Si Automotive Pistons
Authors: Atkinson, Helen V.
Ward, P. J.
First Published: Jul-2008
Publisher: Trans Tech Publications
Citation: Solid State Phenomena, 2008, 141-143, pp. 201-206
Abstract: For hypereutectic Al/Si alloys, one of the advantages of thixoforming in comparison with casting routes is the relatively short processing times at high temperatures and hence limited coarsening of the Si phase. Coarse silicon particles give poor mechanical properties. Here two hypereutectic Al/Si alloys (magneto-hydro-dynamically (MHD) stirred A390 from Pechiney and an extruded A390 alloy from Showa in Japan) have been thixoformed to form pistons. Opening up the die entrance to the full width of the crown made the flow into the die more uniform and helped to reduce the tendency for large pores to form due to swirling of the slurry. Die heating reduced cold shuts in the skirt (thin section) of the piston. Placing inserts into the die to make holes for the piston pins (i.e. having an obstacle in the thicker regions) evened up the flow between the thick and the thin regions in the die. Massive pores experienced in earlier shots were then eliminated. Placing ceramic material in the die entrance considerably reduced the shrinkage porosity in the crown. The use of the Showa alloy, where the globular semisolid microstructure is achieved by a solid state deformation route rather than MHD, gave reduced shrinkage porosity and eliminated macrosegregation of the eutectic and the silicon. Computer modeling has aided optimization of the die.
DOI Link: 10.4028/
ISSN: 1012-0394
Type: Conference paper
Rights: This paper was presented at 10th International Conference on Semi-Solid Processing of Alloys and Composites, S2P 2008, September 16th -18th, 2008, Aachen, Germany and Liège, Belgium and published as Solid State Phenomena, 2008, 141-143, pp. 201-206. The final published version is available at, Doi: 10.4028/
Appears in Collections:Conference Papers & Presentations, Dept. of Engineering
Published Articles, Dept. of Engineering

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