Phase-field lattice Boltzmann study on magnetic-field-assisted dendrite growth of Al-Cu alloy

As a non-contact external field regulation technology, magnetic-field-assisted forming demonstrates significant process advantages and application potential in the field of liquid metal forming. This study established a magnetohydrodynamics multi-scale coupling model based on the phase-field and lattice Boltzmann method. The anisotropy of solute transport behavior during the solidification of Al-Cu alloy under the influence of a magnetic field and its regulatory mechanism on dendrite morphology were investigated. The results indicate that a magnetic field oriented perpendicular to the convection direction inhibits inertia-dominated melt flow through Lorentz force effects. This action diminishes solute distribution asymmetry and facilitates the transition of dendrite morphology from a convection-deflected state to one dominated by diffusion. A transverse magnetic field can suppress gravity-driven solute plumes, thereby eliminating differences in growth rates at dendrite tips induced by natural convection and promoting nearly symmetric dendrite growth. An inclined magnetic field influences the preferred orientation of secondary dendrite arms by altering melt flow direction while accelerating interface instability. Moreover, varying intensities and orientations of the magnetic field can optimize uniformity in solidification microstructure by reconstructing flow field distributions and mitigating solute enrichment as well as the flow field distortion among dendrites.