Understanding the Initial Solidification Behavior for Al–Si Alloy in Cold Chamber High-Pressure Die Casting (CC-HPDC) Process Combining Experimental and Modeling Approach

Abstract

In the cold chamber high-pressure die casting (CC-HPDC) process, alloy solidification in the shot sleeve due to heat loss leads to the formation of externally solidified crystals (ESCs), which have been proven to be closely related to microstructure inhomogeneity and mechanical properties of cast components. In this paper, the solidification behavior of aluminum alloy inside the shot sleeve is studied using a numerical modeling approach. Fluid flow, heat transfer, and solidification of aluminum alloy melt inside the shot sleeve are studied using ProCAST software in three dimensions. A comparison between modeling and experiments shows good correspondence. Moreover, the evolution and distribution of ESCs in the shot sleeve along with their dependence on the piston motion profile are analyzed accordingly. The results show that after the melt impinges the shot sleeve wall, a thin layer of initial solid forms on the wall with a non-uniform distribution along the sleeve in both the longitudinal and radial directions. With piston movement, the initial solid fraction first increases and then decreases to some extent before being injected into the die cavity. The amount of ESCs at the melt free surface are quantitatively analyzed and validated for different piston motion profiles. The results of this work would be useful in further microstructure and mechanical property variability study of high-pressure die casting products.