The production process of globular structure of semisolid metal was investigated. The globular stucture was obtained by mechanical stirring of molten metal during solidification. This process has been identified as rheocasting. In this work, a rotating steel rod was immersed in molten metal of Al-6.23% Si alloy. The rod cools the alloy below its liquidus temperature to intiate solidification while stirring the melt. The rod stirred the melt for short periods and then removed. Effects of rod immersion and removal temperature on morphology of globular structure was studied. Shape factor used to quantify primary α morphology. Shape factor value 1 refers to perfecly spherical morphology and value close 0 for very complex shape Results show that rod immersion and removal temperature had no significant effect on sphericity of primary α. Increasing of rod immersion temperature from 635 oC to 655 oC slightly decreased shape factor from 0.638 to 0.624. While increasing of rod removal temparature from 600 oC to 618 oC slightly decreased shape factor from 0.660 to 0.621. The semisolid metal obtained in this research immediately solidify after the rod removal so that it was unsuitable for direct shaping by die casting.
Keywords: Rheocasting, semisolid metal, globular structure
