IJSRSET1844239 | Received : 20 March | Accepted : 31 March 2018 | March-April-2018 [(4) 4 : 784-787] © 2018 IJSRSET | Volume 4 | Issue 4 | Print ISSN: 2395-1990 | Online ISSN : 2394-4099 Themed Section : Engineering and Technology 109 Rheological Behaviour of Semisolid A356 Alloy Slurry during Cooling – An Overview Sudip Simlandi Department of Mechanical Engineering, Jadavpur University, Kolkata, West Bengal, India ABSTRACT In present days, the semisolid metal forming (SSF) is an emerging casting technique for producing critical automotive, military and aerospace components. The essence of the SSF process relies primarily on distinct rheological behaviour of the alloy during casting under shear. The rheology of slurries has to be properly understood for successful implication of the SSF process. In this work, the author presented an overview of the rheological behavior of semisolid A356 alloy under cooling. The author discussed on model for evolution of structural parameter and apparent viscosity of the semisolid slurry under cooling. Keywords : Solidification, Stirring, Semisolid slurry, Rheology and Apparent viscosity I. INTRODUCTION In different applications of casting, dendritic microstructure is not desirable as it results in poor mechanical properties. One of the ways to suppress this dendritic growth is to augment the fluid flow in the mushy zone by stirring (Spencer et al. [1], Vives [2], Joly and Mehrabian [3], Flemings [4]). The enhanced fluid flow detaches the dendrites from the solid-liquid interface and carries them into the melt to form slurry. When this slurry solidifies, the microstructure is characterized by globular, non- dendritic primary phase particles, separated and enclosed by a near-eutectic lower-melting second phase. The globular microstructures in the semisolid range offers less resistance to flow even at high solid fraction. The above principle is the basis of a new manufacturing technology called the “Semi-solid forming” (SSF). This SSF process offers significant benefits in product quality and productivity, primarily because of the non-turbulent filling of the die, which results from controllable viscosity of the semi-solid slurry. Since flow stress, shrinkage porosity and thermal stress are also lower, the SSF process has the capability of forming intricate and near-net- shaped parts. Recently, the SSF process is a developing technique in India and much effort has been given to commercialize the technique. There are two basic forming methods of the SSF process, namely Rheocasting and Thixocasting (Flemings [4]). In a typical rheocasting process, the semi-solid slurry is prepared in presence of stirring directly beside a die and the slurry is immediately cast into parts in the die. On the other hand, in the thixocasting process, the billets having non-dendritic microstructure are first produced through a direct chilled (DC) casting operation along with stirring. These non-dendritic billets are called „raw materials‟ for further processing. Subsequently, this raw material is reheated to a temperature in the “mushy” zone and processed into final parts using a die-casting machine. The continuous casting in presence of stirring involves cooling, solidification of the melt, fragmentation of dendrites at the solid-liquid interface and the transport of fragmented dendrites in the bulk liquid, and finally the formation of semi-solid slurry which have distinct rheology. The transport phenomenon during the solidification process in presence of stirring is fairly complex because of the movement of fragmented dendrites and the distinct rheological