Effects of Casting Conditions and Deformation Processing on A356 Aluminum and A356-20 Vol. % SiC Composites

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Abstract
An A356 aluminum-20 vol. % SiC composite and an unreinforced alloy were processed using either sand casting or squeeze casting techniques, followed by hot deformation processing via swaging. Hot deformation processing was conducted to reduc tions of 33, 50, 73, 90 and 95 % for both the unreinforced and composite specimens prior to aging to peak strength. The evolution of the microstructure and tensile properties were evaluated for the cast materials in each of the hot worked conditions. The squeeze cast composite exhibited a more homogeneous microstructure in comparison to the sand cast microstructure, while hot deformation produced additional changes in the microstructure of the composite. Deformation processing of the sand cast composite resulted in banding of the aluminum and the SiC particles within the microstructure; such features were not apparent in the squeeze cast microstructure. The tensile strength of the squeeze cast materials exceeded those of the sand cast for both the unreinforced and composite forms, while increased amounts of deformation were shown to improve the ductility of the com posite. Swaging to 95 % reduction produced an increase in the reduction of area from 2.7 % to 14.2 % for the squeeze cast composite and from 0.1 % to 11.0 % for the sand cast compos ite. The results are discussed in light of the microstructural changes accompanying the various processes employed.