Modeling of structural breakdown during rapid compression of semi-solid alloy slugs

Under normal thixoforming conditions, the semi-solid slugs experience a rapid compression before flowing into the die cavity. During a very short time interval, they experience intense shear thinning and their flow behaviour changes from one resembling a solid to that of a viscous liquid. In this paper, a technique of rapid compression testing is outlined, carried out under conditions similar to normal thixoforming. Experimental results are combined with modelling the behaviour of these slurries in FLOW-3D, in order to derive the now parameters. The special properties of semi-solid metals are described using a thixotropic rheological model in which viscosity is a function of shear rate, solid fraction and time.