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Indexed by:期刊论文

Date of Publication:2014-09-01

Journal:China Foundry

Included Journals:SCIE

Volume:11

Issue:5

Page Number:423-427

ISSN No.:1672-6421

Key Words:semisolid slurry; damper cooling tube; microstructure

Abstract:To produce a high quality semisolid slurry that consists of fine primary particles uniformly suspended in the liquid matrix for rheoforming, chemical refining and electromagnetic or mechanical stirring are the two methods commonly used. But these two methods either contaminate the melt or incur high cost. In this study, the damper cooling tube (DCT) method was designed to prepare semisolid slurry of A356 aluminum alloy, and was compared with the low superheat casting (LSC) method - a conventional process used to produce casting slab with equiaxed dendrite microstructure for thixoforming route. A series of comparative experiments were performed at the pouring temperatures of 650 degrees C, 638 degrees C and 622 degrees C. Metallographic observations of the casting samples were carried out using an optical electron microscope with image analysis software. Results show that the microstructure of semisolid slurry produced by the DCT process consists of spherical primary alpha-Al grains, while equiaxed grains microstructure is found in the LSC process. The lower the pouring temperature, the smaller the grain size and the rounder the grain morphology in both methods. The copious nucleation, which could be generated in the DCT, owing to the cooling and stirring effect, is the key to producing high quality semisolid slurry. DCT method could produce rounder and smaller alpha-Al grains, which are suitable for semisolid processing; and the equivalent grain size is no more than 60 mu m when the pouring temperature is 622 degrees C.