Free dendritic growth model incorporating interfacial nonisosolutal nature due to normal velocity variation

Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion, an extended free dendritic growth model was analyzed. Compared with the predictions from the dendritic model with isosolutal interface assumption, the transition from solutal dendrite to thermal dendrite moves to higher undercoolings, i.e., the region of undercoolings with solute controlled growth is extended. At high undercoolings, the transition from the mainly thermal-controlled growth to the purely thermal-controlled growth is not sharp as predicted by the isosolute model, but occurs in a range of undercooling, due to both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion. Model test indicates that the present model can give a satisfactory agreement with the available experimental data for the Ni–0.7% B (mole fraction) alloy.