Phase Field Simulation Of Semi Solid Spherical Dendritic Formation Process

The key of semi-solid forming technology is the preparation of the semi-solid slurry,and the formation of globular structure is a hot research topic in the research of physicists and materials scientists. The morphology of the material microstructure determines the properties of materials. To study the process of the dendritic growth is important to improving material properties. The phase field method, as a mature numerical simulation method, can effectively simulate the formation process of the microstructure in the equilibrium state.In this paper, the KKS phase field model is the fundamental, and the phase field model coupled the flow field and the solute field. With the characteristics of semi solid structure,the nuclei spin is introduced,and solving the mass and momentum control equations.The control equations are solved by different discrete method. Finally, solving the discrete control equations by programming solution. Through the data analysis software of the Origin9.0 to analysis the operation datas,and coming out the visualization results.Then, through the visualization results to researching the impact of each factor on dendritic morphology and solute distribution. In this paper, the numerical simulation of binary alloys and ternary alloys is carried out, and studied the process of the semi-solid spherical structure.The results showed that: the dendrite spin is the key of the transformation from the dendritic to the rose. The flow field make one side of dendrite grow faster and the other side grew more slowly,and the dendrite spin make it a periodic change so that the dendritic growth in all directions. The increase of the flow rate and the degree of under cooling accelerates the dendrite growth,and promoting the transformation of the dendrite to the rose and become a globular structure at last. The increase of dendritic spin angular velocity make the dendrite arm more bent,so that the dendritic has obvious spin to growth; Whether binary alloy or ternary alloy, the increase of flow rate can promote the growth o f grain, and the two dendrite arm growth more obviously. The decrease of the initial temperature increases the degree of under cooling,so that accelerate the diffusion rate of solute in the alloy,and the dendrite growth accelerated.