5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

In modern automotive structural components, metal sheets are combined with casting parts to enable a light and mechanical stable structure. In this study, the bonding between steel metal sheets and aluminum casting parts are achieved as part of the high pressure die casting (HPDC) process. In this way additional bonding steps like welding can be omitted. Gas enclosure at the interface between metal sheet and casting part may hinder a strong bonding. This effect is supposed to be enlarged by the rapid solidification at the interface between sheet and casting, where hot melt hits a cold metal sheet. Cooling rates are in the range of 1000 K/s. Such a rapid solidification leads to a stop of the melt flow already during the filling process and can trap gas enclosure at the interface. Coupled flow and solidification simulation is used to analyze the hybrid casting process with a focus on the wetting of the metal sheet by the melt and the formation of a strong bonding during solidification. Standard solidification models, based on a fraction solid curve, cannot describe essential phenomena of fast solidification, like undercooling of the melt. These phenomena may have a strong effect on the stopping of the melt flow and, hereby, the gas enclosure. Therefore, an advanced rate based solidification model is developed to address non-equilibrium aspects of the fast solidification and enable a more realistic simulation of the bonding process during solidification. The solidification model is calibrated by microstructure simulations using the multiphase-field method. The simulation results are validated against experiments performed on a cold-chamber HPDC machine (Buehler H630-SC) using simplified test geometries.