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The solidified material microstructure formation during solidification decision its final performance, effectively control the microstructure formation during solidification processes have important theoretical and practical significance. Convection in the solidification process is inevitable, and affect the solidification microstructure is formed by changing the solute and the temperature of the solid-liquid interface near the distribution. With the development of computational science, coupled phase-field simulation of the flow field has become a hot research scholars at home and abroad. Dendrite solidification process is the most common microstructure, In this paper, the coupled flow field phase-field model to simulate the solidification of dendritic growth, dendrite growth mechanism under forced convection, quantitative analysis of the presence or absence of forced convection dendritic tip growth behavior has laid a good theoretical basis for effective forecasting and improved material performance. In the the Wheeler phase field model based on coupling temperature field and flow field forced convection pure substance phase-field model of dendrite growth; further coupled solute forced convection binary alloy dendrite growth phase-field model . In the numerical solution, the choice of the governing equations based on a uniform grid finite difference discrete, in order to avoid the restrictions of the time step, and improve computational efficiency, temperature field equations with alternating explicit-implicit method for solving. Using Visual C language simulation program preparation, direct Tecplot visualization program phase-field model calculation program integrated phase-field method microstructure simulation visualization software system. Use of the forced convection pure substance phase-field model, pure Ni, for example, the simulation of a pure substance forced convection single dendrite and dendrite growth and evolution. The results show that the single dendrite growth, the countercurrent dendrite arm rapid growth and downstream dendrite arm slow growth the the horizontal dendrite arm upstream side and the downstream side of the growth there are also significant differences by force; multi-dendrite growth current, crystal structure, characteristics and the joint action of the growth space, the first growth direction just point to the upstream-side external area of ??the dendrite arm growth are promoted, and the main branch and branch developed, other preferential growth direction of dendrite arm growth were inhibited , the main branch and branch degradation, the dendrite growth Succinonitrile the simulation results with gravity convection morphology consistent. Binary alloy phase field model forced convection, Ni-Cu alloy, for example, simulation of forced convection binary alloy single dendrite and dendrite growth and evolution. The results show that forced convection countercurrent dendrite arm received cold melt erosion, low solute concentration and temperature of the dendrite arm tip, the actual supercooling, the dendrite arm rapid growth; enrichment on the downstream side of the heat and solute downstream branch crystal arm of state-of-the-art solute concentration and high temperature, actual supercooling, the dendrite arm slow growth. Multiple dendrites, growth, the interdendritic internal region dendrite arm growth is mainly affected by adjacent dendrite control, the dendrite arm away from the border outer region growth is mainly controlled by the flow field. DC electric field simulation results with synchrotron radiation X-ray imaging observed Sn-Bi alloy dendrite growth morphology. Using to adapt to the the hcp crystal system of the binary alloy phase field model, simulation studies AZ91D magnesium alloy solidification pure diffusion and forced convection single dendrite and dendrite growth process. The results showed that pure diffusion conditions, the dendrite showed significant six-party opposite sex, the direction of balanced growth; forced convection, the direction of the fluid upstream side of the dendrite arm than the 3 direction of the fluid downstream side branches Crystal arm fast growth, each dendrite arm length there is a big difference. Initial stage of growth in a multi-grain, grain growth independently for the rules of a regular hexagon; solidification regular hexagon the grains gradually developed into a dendrite, opposite the growth of dendrite arm influence each other and competitive growth, different branches crystal dendrite arm suppress each other, eventually forming the asymmetric dendrite morphology. The simulation results are close to the actual dendritic morphology. Sigma = of σ0 [εkcos (kθ)] form of the interfacial energy anisotropy function correction, the correction phase field model, in the case of pure diffusion Si dendrite growth morphology simulation study and compared with the experimental results on the basis of, for example, Ni-Cu alloy under pure diffusion and forced convection high interfacial anisotropy binary alloy dendritic growth forecast. The results showed that in high interface anisotropy pure Si dendrite growth, the growth of the part of the crystal to a diagonal direction disappear the primary dendrite secondary dendrite tip edges, which have the typical angular definitions, simulation results with experimental The results are consistent. High surface tension anisotropy in the Ni-Cu alloy dendrite growth, when the surface tension anisotropy strength ε4 lt; 1/15, with increasing epsilon4, the dendrite tip velocity increases, and in close to 1/15 reaches the maximum value; when the ε4 = 1/15, the dendrite cutting-edge speed a decrease of 4.34%; when the epsilon4 is to further increase the, the dendrite cutting-edge speed increased first and gradually decreases after the the to the greatly value. Interface kinetic anisotropy is introduced, the interface only interface kinetic anisotropy delta, the solid-phase class rectangle along the lt; 110 GT; direction of growth; interface exists delta, epsilon4 and there is only epsilon4, solid phase dendrite along lt; 100 GT; direction of growth. In the a flow rate of the the the forced convection of of the 6.43 m / s under the action of, the dendrite the counter-current side of who have received cold melt erosion, the countercurrent dendrite arm the rapid growth of, with compared to when the with the pure diffusion in steady state via an increased growth rate 12.61%; heat and of solute in as above. By Shun stream-side aggregation, downstream dendrite arm slow growth, reduced by 14.62% compared with the pure diffusion steady-state growth rate.
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