Work

Heat transfer behavior and casting solidification characteristics in multi-material functionally structured sand molds

Year: 2026

Type: article

Abstract: The heat-transfer behavior of the casting–mold system directly affects the cooling rate, solidification evolution, and microstructure formation of castings. For complex castings with variations in wall thickness and local hot spots, different regions require different heat-dissipation intensities to regulate the local solidification process. However, conventional solid silica-sand molds mainly dissipate heat through internal heat conduction and provide limited capability for spatial regulation of heat extraction, making it difficult to meet such localized cooling requirements. To address this limitation, this work decomposes the casting heat-release process into three stages: interfacial heat extraction, internal heat conduction within the sand mold, and external convective heat dissipation. On this basis, a multi-material functionally structured sand mold consisting of a chromite-sand inner layer and a Gyroid lattice heat-dissipation outer layer was proposed. Numerical simulations and casting experiments were combined to investigate the effects of material partitioning, functional structure, and external cooling conditions on the heat-transfer behavior, cooling rate, solidification evolution, and grain size of EV31A magnesium alloy castings. The results show that the chromite-sand inner layer enhanced interfacial heat extraction and internal heat diffusion, shortening the solidification time by approximately 35% and increasing the peak cooling rate at 0.1 mm from the casting–mold interface to 132 K/s. The cooling effect associated with the Gyroid structure was strongly dependent on the external convective boundary. Under forced convection, the multi-material functionally structured sand mold increased the average cooling rate to 0.96 °C/s, approximately 96% higher than that of the conventional solid silica-sand mold, and reduced the average grain size from 127 μm to 58 μm. These results demonstrate the feasibility of coordinating mold-material distribution, functional structure, and external cooling conditions to regulate heat-transfer pathways and casting solidification, providing a potential thermal-management strategy for castings with spatially nonuniform cooling requirements.

Source: International Communications in Heat and Mass Transfer

DOI: 10.1016/j.icheatmasstransfer.2026.112699