Effects of engineered cooling based on hollow sand molds on microstructure and properties of aluminum alloy castings

The aerospace and automotive sectors have seen a remarkable increase in demand for high-end light alloy castings, driven by the ongoing pursuit of lightweight. The ability to regulate the solidification and cooling processes of high-end castings is of paramount importance, as it has been demonstrated to enhance the mechanical properties of castings and reduce the occurrence of defects. To explore the efficacy of engineered cooling in optimizing the solidification and cooling process of low-pressure aluminum alloy casting, this study investigates the impact of various engineered cooling strategies on the solidification time, microstructure and mechanical properties of the fabricated castings. The findings indicate that the implementation of adequate engineered cooling strategies can effectively regulate the cooling rate and solidification time of castings. Local heat insulation based on hollow sand mold can delay the solidification and cooling process of castings, while local enhanced cooling utilizing water-saturated resin can moderately accelerate the solidification and cooling process. The combination of these two cooling strategies are demonstrated to facilitate the achievement of sequential solidification in castings. Furthermore, a rational cooling strategy enhances the solidification shrinkage feeding, thereby leading to an improvement in microstructure and mechanical properties of castings. In low-pressure sand casting process, the presence and distribution of pore defects within castings usually exert a more substantial influence on mechanical properties than the grain size. This study provides a theoretical foundation and practical guidance for the optimization of cooling strategies in context of low-pressure sand casting, with the objective of improving the quality and performance of castings.