Influence of Casting Route on the Microstructure and Mechanical Behavior of A360 Aluminum Alloy: A Process–Structure–Property Correlation

This study comprehensively examines the effect of casting route—sand versus permanent mold—on the microstructural evolution and mechanical performance of A360 aluminum alloy produced under identical alloy composition. The objective was to elucidate how differences in cooling rate and solidification kinetics affect dendritic morphology, eutectic silicon distribution, and the resulting property–structure correlation. The alloy was melted at 730 ± 5 °C under an argon-protected atmosphere and cast using silica–bentonite sand and preheated steel molds (200 °C) under gravity conditions to ensure reproducibility. Optical microscopy revealed that the permanent mold route generated a highly refined α-Al dendritic structure with reduced secondary dendrite arm spacing (SDAS) and a uniformly dispersed eutectic Si network, whereas the sand cast alloy exhibited coarse dendrites and irregular Si clusters. These microstructural distinctions led to clear performance differences: the permanent mold alloy achieved approximately 18 % higher Brinell hardness and 10–15 % higher tensile strength while maintaining comparable elongation. Furthermore, its Charpy impact energy increased from 4.81 J to 5.07 J, reflecting superior energy absorption and fracture toughness due to finer and more homogeneous solidification morphology. The findings emphasize that controlling the casting process—specifically through enhanced cooling rate—can significantly strengthen A360 alloy without any chemical modification or heat treatment. This study provides fundamental insight into the process–structure–property relationship and offers a practical reference for sustainable design and manufacturing of high-integrity aluminum components for automotive and aerospace applications.