They could also use stirring to form special solid ingots that parts manufacturers could buy, remelt, and cast. Parts manufacturers would no longer need to handle fully molten metal. Cast or forged components made of iron or steel began being replaced by components of aluminum alloys manufactured by semisolid processing. The advantages of semisolid processing over traditional methods have proved remarkable. Castings of semisolid rather than molten metal form quickly and have lower cooling requirements.
Less gas is entrapped, fewer voids form, the surface finish is smoother, and less shrinkage occurs.
Each year, companies in the United States, Japan, and Europe now produce or use millions of parts made by semisolid processing, and the number is growing quickly. However, as often happens, the commercial adoption of the new process has far outpaced the development of a detailed understanding of how it works. An Energy Laboratory team including Professor Flemings, Anacleto de Figueredo, and Yusuf Sumartha has been performing rigorous experiments to answer such questions. While the focus is on expanding fundamental understanding, the results will have practical implications, providing manufacturers better control over the process and the products it yields. To understand why stirring changes the behavior of semisolids, one must consider the microstructure of solidifying metals.