Simulation Of Dendrite Growth Of Binary Alloy Using Phase-field Method

The characteristic of most engineering materials is closely connected with the microstructure during their solidification process. Therefore how to control the metal solidification process has became a main research point to the materials science.There are various complicated processes in the solidification such as heat transfer,fluid flow and mass diffusion and so on. For the reason of the complicity in these processes, it is very difficult to research the dendrite growth process in practical methods. With the development of the computer technology, numerical simulation of the microstructure of metal solidification process has become one of the most effective methods for the investigation of dendrite growth process. Since the nineteen eighties, the phase field method with its simple characterization methods and the adaptability on various tissues has become one of the most important means on the study of microstructure of growth. This method is based on Ginsburg-Landau phase transition theory. By introducing a phase field variable j, j =1 represents the solid phase and j =0 represents the liquid phase, besides the intermediate value represents the interface. Through coupling the phase field equation with temperature control equation and solute composition equation, this method can very effectively simulate the solidification process of the alloy. Then we use phase field method as a basic method to study the dendrite growth process of alloy.First, the development process of phase-field method and the theories of phase transition and the phase-field simulation means have been introduced. Then, a phase-field model of binary alloy was established based on the principle of entropy increase and the laws of thermodynamics. The growing processes and morphology of Zn-Al alloy dendrite was simulated by using the phase-field method. We used the method of controlling variables to discuss the effect of the anisotropic strength and the interface kinetics coefficient and the interfacial energy and the temperature gradient on dendrite morphology. From the result, got following conclusions:1) With the increase of anisotropy strength the rate of dendrite growth increases and the secondary arms appear to be more easily grown up.2) With the increase of the interface kinetics coefficient the rate of dendrite growthincreases.3) With the increase of the interfacial energy the rate of dendrite growth increases.4) The temperature gradient has influence on the appearance of secondary armsduring the dendrite growing. With the increase of temperature gradient, the rate of dendrite growth increases. But there is no rule of the increase.