The 3D Simulation Of Binary Alloy Solidification Based On Phase Field Method

The alloy solidification is a complex process in macroscopic and microscopic. This process contains the transmitting of heat, the transmission of solid and the releasing of latent heat. And it also contains the nucleation and the growth of crystal nucleus, the dendrites competitive growth and the solute redistribution in micro scale. All of these processes have a great influence on the material properties. The numerical simulation on the process of solidification and the study of evolution of microstructure can let us get a deep understanding on the influence on dendrite growth by different influencing factors. It will in favor of process designing. The Phase-field model uses the diffusion interface model, avoiding tracking S/L interface. This method had a great development at past few years.In this paper, we used a Karma thin-interface model which contains a parameter as anti-solute trapping to study the solidification under isothermal of Fe-1.0wt.%C alloy and study the influence on morphologies of dendrites,solute microsegration and dendrite growth by different parameters. Concludes as follows:(1) We simulated the process of dendrite growth of Fe-1.0wt.%C and obtained themorphologies of dendrite and observed the processes of coarsening and remelting of thesecondary arms. We introduced the solute trapping current, studied the solute distributionwith solute trapping. We concluded that the central of primary stalk had the lowestconcentration and the concentration enriched at the secondary arm spacing. Because themodel neglects the influence of solute gradient on solute distribution, the velocity ofinterface had a seriously fluctuates with the time. And this fluctuate will make a fluctuateof equilibrium partition coefficient k. Therefore, the solute concentration in the dendritewas heterogeneous.(2) With the dendrite growing,the tip velocity decreased from a maximum value first andcame into a steady state at last.The tip radius had an opposite change with the tip velocity.The tip radius and tip velocity are convergent.(3) The supersaturation had the same influence as the undercooling when it was less than 0.55.When ? >0.55, the morphology of dendrite became irregularly. With the supersaturationincreasing, the kinetic control has an opposite influence on solute redistribution with thesolute control. When ? <0.55, it occurred a seriously microsegration with thesupersaturation increasing. When ? >0.55, the microsegration became reduced. Therefore,it could be reduce microsegration by increasing supersaturation in producton.(4) The anisotropy coefficient had a great influence the process of solidification, theanisotropy coefficient can promote the dendrite growth. With the increasing of anisotropy,the disturbance might easily amplify and the morphologies of dendrite had a complexmorphologies.(5) The noise would have a little influence on dendrite growth, it will make the side branch ofdendrite unstably. This kind of unstability would lead to an energy fluctuation. Thefluctuation could change the solute distribution and then had an influence on side branchgrowth.