Effects of modification during conventional and semi-solid metal processing of A356 Al-Si alloy

Abstract

Silicon is one of the most significant alloying elements incorporated in Al-alloys. Its addition is to improve castability, fluidity, reduce shrinkage and to render superior mechanical properties. The morphology of silicon however plays an important role on the mechanical properties of finished products. Therefore, the common practice is to modify the as-cast flake or acicular silicon morphology employing special heat treatment or addition of certain modifiers. As a result, the silicon morphology changes to fibrous form with enhanced mechanical properties of the as-cast parts. For conventional casting, Si modification has been investigated widely by many researchers but in the semi-solid metal (SSM) processing, few published papers could be found. The purpose of this contribution is to report the effects of Sr addition as a modifier to 356 alloys for both conventional and SSM casting routes. The swirled enthalpy equilibration device (SEED), slurry-on-demand process was used to cast SSM billets. A comprehensive set of data is presented to characterize microstructural evolution of the as-cast SSM billets.