Design of micropit surface geometries for inhibiting molten aluminum wetting on ductile iron

Abstract

Engineering microstructural surfaces represents a primary strategy for mitigating wetting-induced adhesion of molten aluminum in ladle siphoning tubes. Based on geometric conditions and force balance principles under wetting conditions, a mathematical relationship between the geometric parameters of micropit structures and the apparent contact angle was established using the Young-Dupré equation. The volume of fluid (VOF) method was employed to numerically simulate the dynamic wetting behavior of molten aluminum on surfaces with varying micropit dimensions. Simulation results demonstrate that increasing the micropit diameter, decreasing the spacing, or increasing the depth leads to a corresponding increase in the apparent contact angle, indicating suppressed wettability of the aluminum liquid. This trend aligns with theoretical model predictions, validating the effectiveness of the model. Subsequently, the microstructural dimensional parameters were optimized using response surface methodology. Micropit arrays were fabricated on ductile iron substrates via laser processing. Wetting experiments with molten aluminum at 900 °C showed that the measured contact angles were significantly higher than those on smooth surfaces, confirming the pronounced wetting-inhibition effect of the micropit structures. Interfacial analysis revealed that reactions between aluminum and iron resulted in the formation of an intermetallic compound layer that substantially exceeded the depth of the micropits.