SPH Model Approach Used to Predict Skin Inclusions into Semisolid Metal Castings

Semisolid metal processing of metallic alloys takes advantage of the thixotropic behavior of material with non-dendritic microstructure to produce near-net-shape components with improved mechanical properties. The much higher apparent viscosity of the semisolid billet limits the risk of oxide formed on the free surfaces to become incorporated into the easting during the process. But, the external-skin on the periphery of the billet, which is often partially solidified and contaminated with lubricants, should not be included into the casting as this can be a cause of reject for most structural parts. In this paper, a preliminary model is set-up using the LS-DYNA SPH formulation to follow the paths of the skin. Calculations carried out show that this approach appears to be very promising to predict the paths of contaminated skins into semisolid castings. It can then be utilized to design suitable molds and gating systems.