MODELING OF 'BANDING' MICROSTRUCTURE FORMATION IN CENTRIFUGALLY SOLIDIFIED Ti-6Al-4V ALLOY

Numerical investigations of the ’banding’ microstructure formation during solidification of Ti-6Al-4V alloy in the centrifugal casting are conducted using a multi-scale model, which combines the finite difference method (FDM) at the macroscale with a cellular automaton (CA) model at the microscale. The macro model is used to simu- late the fluid flow and heat transfer throughout the casting. The micro model is used to predict the nucleation and growth of microstructures. With the proposed model, numerical simulations are performed to study the influences of the nucleation density, mould rotation speed, and casting size upon the ’banding’ microstructure formation. It is noted that changing the nucleation density has a minor effect on the microstructure formation. The rotation speed promotes the formation of ’banding’ microstructure, which is more noticeable for larger size castings. The major mechanism responsible for this ’banding’ phenomenon is the spatial variation in cooling rates created by centrifugal force.