Development of an Advanced Rheocasting Process and Its Applications

Among semisolid forming processes, increasing attention has now been focused on the commercialization of casting processes based on rheocasting in aluminum automotive casting fields because of its advantages compared to thixoforming, in regards to the efficiency in cost and productivity, and mechanical properties. In this paper, an advanced rheocasting process is introduced, which has been developed recently at Yonsei University and is now on the way to practical uses in Korea and Japan. In this method, the semisolid slurry production is based on the nucleation method, in which the nuclei of primary
phase formed in the melt are prevented to grow into dendrites, instead they grow into fine globular particles to become semisolid slurry having rheological behavior. By increasing the number of nuclei, very fine and uniform globular microstructures can be obtained, resulting in an increase of mechanical properties. Recently, commercial rheo-diecasting machines based on the present method have been developed, and now are being used in manufacturing aluminum automotive casting parts. Furthermore, the present method is now being tested to investigate its possibility of application to various alloy systems.