Numerical Simulation Of Dendritic Growth Of NI-CU Binary Single-phase Alloys Using A Phase-field Method

Phase-field method can be used to describe the complicated morphologies of dendritic growth without explicitly tracking the complex phase boundaries. It is expected as a powerful tool to describe complex phase transitions in non-equilibrium state. It is the frontier domain of the numerical simulation during solidification processes at present.The dendritic growth in the solidification of alloy is simulated by the phase-field method, the mechanism of the dendritic growth during solidification of the alloy is discussed, and a favorable base for prediction of mechanical property of casting is established. The governing equations are discretized on uniform grids using the Finite Difference method, and a double grid method is used for the mesh slice. The thermal governing equation is numerically solved using an alternating direct implicit (ADI) method, which is unconditionally stable, irrespective of the time step employed. The narrow solid/liquid interface method and the capturing solute diffusing boundary method are put forward to optimize the numerical computation of the phase-field model.The free growth of dendrite in the solidification of Ni-Cu binary alloy are simulated on the isothermal condition, the competitive growth of the secondary arms, ripen and solute microsegregation in the free dendritic growth are realized. The dendritic growth of alloy solidification is simulated using the non-isothermal model with Neumann boundary conditions, and the effect of undercooling on the dendritic growth is studied. With the decreasing of freezing storage temperature, the dendrite growth rate of the dendrite faster, secondary crystal arm more developed, and solute segregation moreserious, but when the temperature drops to the critical temperature 1569K, micro segregation lowers quickly.More grain results and single grain are not the same. When the dendrite interaction, dendrite growth is suppressed, bending, dendrite no longer symmetrical. More grain simulation of Continuous nucleation model and real situation is approaching. In the directional conditions, flat interface chip cell instability, cellular crystal spacing gradually adjusted, and finally the steady growth of cellular crystal spacing is about 1.8 um. As the initial temperature decrease, interface gradually from the columnar crystal to the cellular crystal to flat interface evolution.