Numerical Simulation and Experimental Validation of Nondendritic Structure Formation in Magnesium Alloy Under Oscillation and Ultrasonic Vibration

In this study, the formation of nondendritic structures in the primary phase of magnesium alloy solidified under oscillation and ultrasonic vibration was investigated by numerical simulation and experimentally. The growth and motion of a dendrite during solidification was simulated by a combination of the lattice Boltzmann method and the phase-field method. The simulation and experimental results indicated that higher oscillation amplitudes and acoustic streaming made the microstructures change from dendritic to nondendritic in the α-Mg primary phases. A sufficient shear stress and an appropriate flow time in the barrel should be satisfied when a given inclined angle is selected. The effects of the flow and the thermal field on the nucleation behavior, the constitutional undercooling, and the growth morphology are also discussed. It was found that a high shear rate and high turbulence can help homogenize the temperature and the concentration fields and collide and rotate the α-Mg primary phases.