Regulation Mechanism of Cusp-Magnetic-Field-Induced Thermoelectric Magnetic Convection on Dendrite Refinement and Uniformity in Single-Crystal Superalloys

The refinement and uniformity of dendrite microstructures in single-crystal (SC) superalloys directly determine their high-temperature mechanical properties and service reliability. In conventional directional solidification (DS) processes, the macroscopic temperature and solute fields ahead of the solid−liquid (SL) interface are inherently spatially non-uniform, resulting in pronounced variations in primary dendrite arm spacing (PDAS) at different locations. This poses a significant challenge to achieving effective control over the overall uniformity of the solidification microstructure. In this study, leveraging the unique configuration of the Cusp magnetic field (CMF), we investigated its influence on dendritic growth behavior in directionally solidified SC superalloy specimens with different diameters. The results demonstrate that the CMF reduces the PDAS and improves its spatial distribution uniformity. Moreover, both effects are enhanced with increasing specimen diameter. Quenching experiments combined with macroscale multiphysics simulations reveal that thermoelectric magnetic convection induced by the CMF effectively compensates for the non-uniform thermal field from radiative heat transfer, thereby driving the macroscopic interface toward a planar morphology. Phase-field simulations further indicate that, the differences in dendrite tip migration kinetics at different positions are reduced under the relatively planar interface, thereby synergistically promoting dendrite refinement and homogenization. This work provides a new theoretical basis for the dendrite refinement and homogenization in SC superalloys through macroscopic SL interface engineering.