Study of macroscopic segregation in ingot considering the movement and growth of equiaxial crystals

The solidification process of alloy ingot is often accompanied by the phenomena of free dendrites growing and colliding with each other while moving, which has a non-negligible influence on the temperature field, flow field, solute field and microstructure of the ingot, and it is one of the key issues in the study of ingot solidification organization formation. The cellular automata-lattice Boltzmann (CA-LB) coupling model has been developed rapidly in recent years in dealing with the moving dendrites, which can not only maintain the morphology of the moving dendrites well, but also calculate the mutual collisions between the dendrites reasonably. In this work, the cell-automata-lattice Boltzmann model for simulating the growth of free dendrites is improved. Alternating direction implicit iteration method is used to solve the differential heat conduction equation, and the simulation parameters are not limited by stability conditions in this method. In this research, the accuracy of the flow-solid coupling of the model is verified by taking the flow around a circular cylinder for example, and the temperature field of the model is well coupled under the natural convection condition. Finally, the solidification process of Fe-0.34%C alloy ingots with or without equiaxed grain movement is simulated using this model. The simulation results show that the movement of equiaxed grains increases the contact probability with the neighboring dendrites, which leads to a more uniform grain size in the ingot; the movement of dendrites also changes the solute distribution in the center of the melt, especially increasing the size and range of the hot-top segregation; the movement of equiaxed grains is impeded by the columnar crystals, and therefore the CET region is not much affected by the movement of dendrites.