Refinement of Primary and Eutectic Silicon Phases in Shape Casting of Hyper-Eutectic Al-Si Alloys

Abstract

Hyper-eutectic Al-Si alloys composed of low-density materials with excellent castablity are good candidates for aerospace and automobile applications. Our efforts over the last few years have demonstrated that such hyper-eutectic Al-Si alloys with no primary silicon phase but with a eutectic microstructure that assumes nano-fibrous morphology for the eutectic silicon phase can be grown by directional solidification. In pursuit of this effort, more hyper-eutectic Al-Si alloys containing ultra-refined primary and eutectic silicon phases have been grown by an alternate casting method known as shape casting. The process of this fabrication and the microstructure of the resulting alloys are presented here.