Macro-micro modeling of solidification

To solve solidification problems, macro-models are generally applied. Macro-micro models, by considering the formation of microstructures in terms of nucleation and growth, can obtain better results than can macro-models. Except for temperature distributions, macro-micro models can offer more information about the solidification process, including undercooling, grain size, grain density etc. These data can be used to predict the mechanical properties of materials directly. In this paper, two macro-micro models are built to investigate the equiaxed solidification of eutectic. One macro-micro model considers the nucleation step, and the other does not (assuming that nucleation occurs instantaneously). An experimental example of a cylindrical casting is used to test these models. The finite difference method is utilized to solve the heat transfer problem, and the source term method is employed to handle the released latent heat. From a comparison with the experimental result, the computed cooling curve is found to be very close to the experimental one. From the computational results, it is found that a higher cooling rate yields the greater undercooling, which leads to a smaller grain size or higher grain density.