Modeling the solidification of functionally graded materials by centrifugal casting

A numerical investigation of the solidification process during centrifugal casting of functionally graded materials (FGMs) is conducted. Focus is placed on the interplay between the freezing front propagation and particle migration. A one-dimensional solidification model, with particle transport taken into account, was developed based on the general multiphase model by Wang (1994). The model equations were solved numerically using a fixed-grid, finite-volume method. The model predictions of temperature and particle volume fraction distributions during solidification were validated against the experimental results of a water/glass-bead system solidified in a rectangular ingot under gravity. The validated model was then applied to centrifugal casting of Al/SiC FGMs in a cylindrical mold. The model shows that there exists a particle-free zone in the inner region of the centrifugally cast ingot, followed by a graded particle distribution region towards the outer wall. The mechanisms for the gradient formation were identified to be the geometry and the angular velocity of the cylindrical mold, and the solidification rate. The effects of the initial particle concentration, particle size, rotational speed, cooling rate and superheat were explored.