Anisotropic wetting of molten Sn on α-Al2O3 in high magnetic fields

High magnetic fields (HMFs) can regulate the wettability of molten metals; however, their effects on diamagnetic melts and the crystallographic-orientation dependence on substrates remains unclear. We systematically investigated molten Sn wetting on α-Al2O3 with different crystallographic orientations under HMFs, used EBSD to quantify grain-size changes, and quantified field effects on interfacial tensions and clarified the mechanism of orientation-dependent wetting anisotropy. Upon application of HMFs, the wettability of molten Sn on α-Al2O3 substrates was enhanced to varying degrees and increased progressively with magnetic flux density. At 6 T, the equilibrium contact angle of the Sn/ α-Al2O3 decreased significantly by 32{degree sign}. Applying HMFs enhanced nucleation and refined grains, with the greatest reduction (~306 μm) observed in the Sn/ α-Al2O3 system. Theoretical analysis and calculations indicated that applying an HMF reduced the liquid-gas interfacial energy and altered the solid-liquid interfacial energy, and that these coupled changes affected the wetting behavior. The orientation dependence of α-Al2O3 susceptibility led to field-induced differences in solid-liquid interfacial tension and hence orientation-dependent wetting. These results reveal a direct link between field-induced changes in contact angle and nucleation enhancement, further supporting the orientation-dependent nature of magnetic-field regulation of wetting behavior.