Prediction of solidification microstructure in γ-TiAl alloy ingots during vacuum arc remelting

A three dimensional cellular automaton-finite element model was developed to predict the solidification grain structures in γ-TiAl alloy ingots during vacuum arc remelting process, in which Gaussian distribution continuous nucleation model was adopted to describe the nucleation and the KGT model was extended to multi-component alloys to account for the growth kinetics of the dendrite tip. Effects of melting rate, heat transfer coefficient and nucleation parameters on the solidified microstructure evolution were investigated. The results reveal that with increasing in the melting rate or increasing in the maximum volume nucleation density, the formation of equiaxed grains is promoted, and the growth of columnar grains is restrained. Larger mean undercooling and larger heat transfer coefficient can increase grains size and number of columnar grain. The effects of variation of standard deviation on grain structure of the ingot can be ignored.