Abstract: A mathematical model for the three dimensional simulation of free dendritic growth and microstructure evolution was developed based on the growth mechanism of crystal grains and basic transfer equations such as heat, mass and momentum transfer equations. Many factors including constitutional undercooling, curvature undercooling and anisotropy, which had vital influences on the microstructure evolution, were considered in the model. Simulated results showed that final microstructural patterns and free dendritic growth could be predicted reasonably and calculated results were coincident with experimental. The simulated results of free dendritic growth indicated that the strength of anisotropy has significant effects on free dendritic growth, dendrite profile, micro solute and temperature distribution. The dendritic grain profiles with fully-grown parallel secondary arm tend to be formed at the intensive anisotropy, while near octahedral grain profiles with small protuberances of surface at low strength of anisotropy. The simulated results of free dendritic growth also indicated that there are small molten pools left in interdendritic areas. This is helpful to understand the fundamental of the formation of microstructure related defects such as microsegregation and microporosity.

Key words: Modeling and simulation, Dendritic grain growth, Microstructure evolution