Simulation And Experimental Research On The Directional Solidification Process Of High Purity Aluminum

High-purity aluminum is widely used in modern industry due to its excellent properties.The key to the development of high-purity aluminum is aluminum purification technology.China is a large producer of high-purity aluminum,but there are still few studies on the purification process and purification mechanism of high-purity aluminum.In this paper,the finite element simulation software ProCAST and the upward-drawn directional solidification furnace are used to carry out numerical simulation and experimental research on the directional solidification process of high-purity aluminum.The self-built model successfully simulated the directional solidification process of high-purity aluminum,and the accuracy of the simulation model was verified through experiments.The effects of the process parameters in the purification and solidification of high-purity aluminum on the axial concentration distribution,radial concentration distribution,and structure morphology of the aluminum ingot are studied by simulation and experiment.Draws the following conclusions:(1)In order to realize the directional solidification process of high-purity aluminum,the simulation model can be realized by using a custom function for transforming the thermal coefficient of the crucible outer wall.It can highly approximate the process of heat preservation in the furnace,cooling of the crystallizer and cooling outside the furnace in the process of directional solidification and pulling of high-purity aluminum.(2)Different initial temperatures have a great influence on the concentration distribution of the ingot,mainly the distribution of elements with k>1 at the initial stage of solidification.The unsuitable initial temperature will affect the temperature gradient at the front of the solid-liquid interface in the initial stage of solidification and directly affect the effect of impurity enrichment.(3)When the interface is slowly advancing with a straight interface,the theoretical purification effect is the best,but the experimental and simulation results show that because the initial edge heat dissipation condition is better than that of the core,and the solidification part in the middle and late stages of solidification,the heat dissipation effect of the solidified part is improved.The process is difficult to maintain a flat interface.Only by calculation and experiment,pulling at an appropriate pulling speed,try to keep the solid-liquid interface to a large degree of supercooling.(4)The best process parameters studied by simulation and experiment should be the initial temperature of 700?,the stirring intensity of 6rad/s,and the pulling speed of 0.0005m/s.Through experiments and simulation studies,it is found that the radial distribution of the solute in the ingot is closely related to the stirring intensity.When the stirring intensity is 6 rad/s,the radial distribution of the solute in the ingot has the highest uniformity.(5)Experimental studies have found that the structure of the ingot is closely related to the distribution of solutes.The crystal grains at the beginning of solidification are mainly columnar crystals.Because the degree of subcooling is smaller than the edge,the crystal grain size is larger.As the solidification process progresses,the crystal grains grow,and until the end of solidification,the crystal grains mainly become equiaxed crystals.