Electronic Resource
s.l. ; Stafa-Zurich, Switzerland
Solid state phenomena
Vol. 141-143 (July 2008), p. 201-206
ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
For hypereutectic Al/Si alloys, one of the advantages of thixoforming in comparison with castingroutes is the relatively short processing times at high temperatures and hence limited coarsening ofthe Si phase. Coarse silicon particles give poor mechanical properties. Here two hypereutectic Al/Sialloys (magneto-hydro-dynamically (MHD) stirred A390 from Pechiney and an extruded A390 alloyfrom Showa in Japan) have been thixoformed to form pistons. Opening up the die entrance to thefull width of the crown made the flow into the die more uniform and helped to reduce the tendencyfor large pores to form due to swirling of the slurry. Die heating reduced cold shuts in the skirt (thinsection) of the piston. Placing inserts into the die to make holes for the piston pins (i.e. having anobstacle 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 dieentrance 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 ratherthan MHD, gave reduced shrinkage porosity and eliminated macrosegregation of the eutectic andthe silicon. Computer modeling has aided optimization of the die
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.141-143.201.pdf
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