EFFECT OF VACUUM ON DIE FILLING IN HIGH PRESSURE DIE CASTING: WATER ANALOG, PROCESS SIMULATION AND CASTING VALIDATION

High pressure die casting (HPDC) of aluminum alloys is increasingly used for thin-walled and lightweight components in automotive and other industries. However, a major concern associated with these castings is gas porosity mostly attributed to air entrapment during the filling process of the high-speed metal injection in HPDC. One approach to reduce gas porosity is to use a vacuum to remove air from the die cavity during the filling process and improve the mechanical properties of the HPDC components. However, quantitative effect of vacuum on porosity formation and fluid flow during die casting has not been sufficiently established to maximize the benefits of vacuum use in the die casting industry. In this paper, water analog experiments were conducted to investigate the effect of vacuum on die cavity fill and porosity formation. The results were compared to MAGMASOFT((R)) flow simulations and X-ray Computed Tomography (CT) scans of HPDC aluminum alloy castings to quantify the reduction of entrapped air and gas porosity at different levels of vacuum. The water analog experiments and simulations show good agreement and demonstrated quantitative benefits of using vacuum in high pressure die casting.