Multi-physics simulation of dendritic growth in magnetic field assisted solidification

Magnetic field assisted casting and welding attracted research attentions in the recent decades because it has been observed that the inter-dendritic flow of liquid metals can be controlled by the imposed external magnetic field. However, the underlying mechanism of dendritic growth under a magnetic field is still not fully understood because of the limitations in in-situ experimental methods. To elucidate the mechanism, a new multi-physics model is proposed in this work to simulate the dendritic growth under the influence of an external magnetic field with the consideration of the natural convection. In this model, the physics of solute transport, phase transition via phase field method, natural convection and thermoelectric magnetohydrodynamics via lattice Boltzmann method are tightly coupled. Simulation reveals that intense thermoelectromagnetic convection occurs in the vicinity of the solid-liquid interface, and vortices are generated between dendritic arms. It is shown that the thermoelectromagnetic convection has a major influence on dendritic morphology. The simulation results help explain the experimental observation of curved solidification front and tilted primary trunks. The simulation model is validated by comparing the microstructure morphology and composition distribution with experimental results.