Influence of static magnetic field on the heterogeneous nucleation behavior of Al on single crystal Al₂O₃ substrate

This paper investigates the heterogeneous nucleation behavior of Al on single crystal Al₂O₃ substrate under the influence of static magnetic field (SMF). The nucleation temperature of the Al melt on the substrate was measured to decrease ~2.9°C under SMF, i.e. the undercooling was enhanced with the application of SMF. Using electric back-scatter diffraction (EBSD) and high-resolution transmission electric microscope (HRTEM), the interfacial crystal orientation matching of Al/Al₂O₃ was found to change dramatically, from {110}[011]Al~//{101¯0}[0001]Al₂O₃ without SMF to ~11.4^o between {110}[1¯12]Al and {101¯0}[0001]Al₂O₃ under SMF, indicating that the SMF can increase the lattice misfit of Al/Al₂O₃ interface. The lattice matching deviation caused by SMF was supposed to lead to the increase of interfacial free energy of the nucleus/substrate interface, and thus the formation of critical nucleus and the undercooling were modified. The results demonstrate that SMF is capable of influencing the heterogeneous nucleation behavior of the melt.