Phase-field Simulation Of Convection On Dendrite Growth

Computer modeling and numerical simulations of dendritic crystal growth plays an important role in prediction and improving material properties to establish the relationship of material properties and material processing with material microstructure.Convection influence on the organization in solidifying is already the fact which allows of no to query. In this paper aimed at simulating single grain and multiple grains growth under the role of forced convective during solidifieation of undercooled melt of pure metal under different condition by using phase-field method.The mechanism of dendritic growth in undercooled melt is diseussed.Based on the coupling of flow and temperature,phase field of phase-field model, proposed by Tong, develops the model which consists of a single-phase control of many grains of dendritic growth, and studies pure nickel metal in solidification process of dendritic growth for the numerical simulation.In the process of simulation, the Visual C++ 6.0 was used to calculate the program and the Tecplot 9.0 was used to achieve the vision of results. In order to save time of calculation and improve the efficiency, an interpolative method is used to achieve the coupling of the macro field and the micro field.First of all, through the analysis of whether or not forced convection case compared dendrite morphology,The growth speeds of each tip in a forced flow are different, the upstream tip is highest,the tip in a horizontal direction normal to the flow comes next, and the downstream tip is slowest. studies of a single dendrite at the preferred growth orientation whether or not convection case dendrite morphology and the speeds of tip.Secondly, studies the influence of forced convection velocity U, the undercooling△, anisotropic coefficientγand the coupling coefficientλon the grain morphologies, calculated under different circumstances the speeds of tip. The results showed that: with the fast of the convection velocity, the growth speeds of the dendrite become larger ,the more obvious advantagest of the speed upstream dendrites ; the larger the anisotropic coefficient y , the thinner the branching are ,when anisotropy is greater than 0.07, the variation of dendrite morphology distortion happened; undercooling in the pure metal dendrite growth process plays a very decisive role, when the undercooling is great, dendrite tip velocity is increased linearly the general trend; coupling coefficient with the increase of crystal morphology by mast～slender sticks crystal, when the artificial amplification, the grain morphology of distortion, Therefore, the value of coupling coefficient is detemined by physical properties .Third, whether or not the convection of pure metal is simulated when many grains in different directions at the preferred growth orientation morphology, The results show that the opposite to each other,when the grains growth will be affected each other, different grains with one another and inhibit the main branch, making a grain length of a main branch length shorter than the other, and its main branch the growth of bending. Also add the case of noise, and promote the growth of secondary dendrites.In this paper, greatly improve the computational efficiency, and the model could present the true solidification process of dendritic growth.