Phase field modeling for dendritic morphology transition and micro-segregation in multi-component alloys

By using the phase field model for the solidification of multi-component alloys and coupling with real thermodynamic data, the dendritic morphology transition and the dendritic micro-segregation of Ni-Al-Nb ternary alloys are simulated in two cases, i.e., varying the alloy composition at a fixed undercooling and varying the undercooling at a fixed alloy composition. The simulated results indicate that with the increase of the dimensionless undercooling U (U=ΔT/ΔT ₀, where ΔT is the undercooling and ΔT ₀ the temperature interval between the solidus and liquidus), the dendritic morphology transfers from dendritic to globular growth in both cases. As to the dendritic micro-segregation, both cases present a regularity of increasing at first and then decreasing.