Simulation of dendrite collision behavior based on cellular automata-lattice Boltzmann model

Abstract

In the alloy solidification process, the movement behavior of free dendrites in the melt is one of the key issues in studying the formation process of the alloy solidification structure. The cellular automata-lattice Boltzmann coupling model has become a main numerical model for numerical simulation of solidification microstructure in recent years. In this paper, cellular automata and lattice Boltzmann model for simulating dendrite growth are improved to simulate the movement of equiaxed grains in undercooled melt. In the improved model, the Galilean invariant momentum exchange method is used to calculate the fluid force, the motion equation of the center of mass is solved to calculate the motion displacement of the dendrite, the motion of the dendrite is realized through the dynamic mesh technology, and the rigid sphere model is used to deal with the collision of the dendrite. The settlement of a single dendrite in the undercooled melt of Al-4.7% Cu alloy, the settlement of two round particles in the Newtonian fluid, and the elastic collision of two dendrites are all simulated by this model. The simulation results show that this model can maintain the morphology of dendrites well in the process of calculating dendrite growth motion, and this model can calculate the collision process of irregular dendrites. The movement of dendrite disturbs the melt around it, resulting in a significant change in the concentration of melt around it, which affects the growth of dendrite and aggravates the asymmetry of dendrite growth.