The Numerical Simulation Of The Drifting Behavior Of Single Crystal In The Melt

In the solidification process of ingots and castings,the drifting and deposition of a large number of grains have an important influence on the composition distribution and the final microstructure,but the numerical simulation of the drifting and deposition has just started in the solidification field.This paper presents a two-dimensional modeling approach for the solidification process of the single drifting dendrite by combining the lattice Boltzmann model and the cellular automaton(LBM-CA).The LBM model is verified by the natural convection and forced convection in a closed square cavity.The simulation results show that the LBM model established reproduces the flow results preferably in this paper.The validity above proves the correctness of the model.The CA-LBM model is used to study the drifting process of pure aluminum grain and Al-Cu alloy grain,and the results are as follows.Firstly,the LBM model is used to simulate the falling process of single particle under natural convection and forced convection.The single particle falls vertically and can not move horizontally in the natural convection,while the particle can fall vertically and move horizontally along the streamline in the forced convection.Secondly,the CA-LBM method is used to study the movement and growth of single pure aluminum grain,1)if the grain holds static under the natural convection,the morphology of the grain is not symmetrical in the vertical direction;2)if the grain falls under the natural convection,the asymmetric growth of the grain is more remarkable in the vertical direction;3)if the grain falls under the forced convection,the grain shows asymmetric growth both in the vertical direction and horizontal direction,and it is more intense in the vertical direction.Finally,the movement and growth of single Al-Cu alloy grain is studied by the CA-LBM method.The results show that the solute distribution is uniform at the initial stage,and the morphology of the grain is asymmetric at last.In addition,the solute is more and more serious with the natural convection.At the initial stage,the solute distribution is uniform.The solute distribution is uneven at last,and the solute concentrates and is more and more extensive at the upper part of the dendrite,but the solute is fewer and fewer at the down part of the dendrite.