Microstructural evolution of electromagnetically stirred feedstock SSM billets during reheating process

Abstract

Semi-solid metal (SSM) processing is an effective alternative to the classical manufacturing processes of casting and forging. The key issue in SSM is the production of suitable feedstock with guaranteed continuous supply. To produce good quality billets, the current work studied the thixocastability of electromagnetically stirred (EMS) Al-7Si alloy billets and compared them with conventionally cast billets to establish the effect of EMS in improving the quality of feedstock. In all cases, the intention was to study the microstructure of the billets just before feeding it into the high pressure die casting machines and therefore the billets were reheated to thixocasting temperature and isothermally held for 10 min before being quenched in water. The outcome of EMS application was the formation of refined and more globular SSM billet structures with less entrapped eutectic. The implication of pursuing such work is to guarantee continuous supply of feedstock to enable the establishment of manufacturing facilities, similar to mini mills for steel industry, where the feed stock is shipped to casting site to be shaped in high pressure die casting machines. © 2013 Springer Science+Business Media New York and ASM International.