Combined analytical/numerical modelling of nucleation and growth during equiaxed solidification under the influence of thermal convection

Equiaxed grain solidification in inoculated melts is modelled on a macroscopic scale. The grain initiation is based on grain refiners present in the alloy melt as in most industrial castings. The Avrami analytical approach is used to model equiaxed growth. The model considers natural thermal convection and grain transportation by the resultant fluid flow. Flow characteristics during solidification are incorporated into the model by considering the equiaxed grains in undercooled liquid initially as slurry and later as a porous medium when it becomes coherent. Solidification of Al-7wt.%Si is simulated for different conditions. Evolution of cooling-curve characteristics are compared with a previous model and found to be in close agreement. The model simulation results suggest that nucleation can continue even after the recalescense. The limitation of grain refinement by recalescense and the potential influence of solutal effects are discussed. Simulated equiaxed grain size distribution and temperature evolution in the presence and absence of convention are compared and contrasted.