Number Simulation And Key Technologies Study Of NiCu Alloy Three-dimensional Dendrite Growth By Phase-field Method

Number simulation of solidification in the casting can help us to understand the solidification mechanism and predict the solidification microstructure, which can optimize the casting process. Based on the two-dimensional simulation program of dendrite growth, A program which is used to simulate three-dimensional grain growth is compiled on the basis of Fortran language,Three-dimensional dendrite growth is simulated.The growth process of three-dimensional dendrite can be divided into two stages. In the first stage, the nuclei in the undercooled melt grow gradually along the main axis; In the second stage, the lateral branches appear at the dendrite primary arm. when the primary dendrite arms grow to the boundary , the growth space will be restricted and the dendrite primary arms will not grow,then the lateral branches grow in competition and coarsen, which tend to fill the whole domain.the parameters of the interface atomic motionτ0 has a great influence on dendritic morphology. When it is very small, solid-liquid interface is instabile, the disturbance of the interface is easy to be enlarged, a complex side branches will be formed, the dendritic shape is deformed, the disturbance can advance the growth rate.Asτ0 increases, the solid-liquid interface becomes stable , a smooth dendrite morphology will be formed.As the undercooling degree is increasing, the tip velocity of the dendrite growth at steady state is become faster; the large the undercooling degree is , the more lateral branches are。Thermal noise have an important impact on interface morphology of the directional solidification , the crystal growth morphology of the cells will transform from the smooth interface to the dendrite cell.The anisotropy parameter is studied in this paper,As the anisotropy increases, the concentration gradient of NiCu alloy dendrite solid-liquid interface increases, when the anisotropy increases to 0.07, because the growth rate of dendrite tip is greater than the diffusion rate of solute atoms, a large number of solute atoms gather in the solid phase , making the concentration of solid phase increases substantially.The phase field and temperature field coupling strength is very important parameter, which determines the heat and the solidification of the links on the grain growth of the role of absolute control. When the coupling coefficient is small, the temperature has little effect on the phase field, the growth rate is the same in all directions, anisotropy is not obvious; with the coupling coefficient increasing, anisotropy is enhanced, the growth rate changes in all directions, the growth rate in axis direction is the largest, The dendrite main branch becomes thin and smooth, the front interface is stable, ,while the temperature field boundary layer is thin.