MODELING OF SOLUTE DRAG IN THE MASSIVE PHASE TRANSFORMATION

Abstract—The role of solute drag in the massive phase transformation is evaluated through the dissipation of Gibbs energy by diusion. As an introduction, the solute drag in grain boundary migration is first examined using the wedge-shaped energy function considered by Cahn and by Lücke and Stüwe. The eect of a diusivity varying from a low value in the bulk to a high value in the center of the boundary is exam-ined. It decreases the solute drag drastically. For the massive phase transformation it is demonstrated how the solute drag increases by the tendency for segregation and by a high diusivity in the interface but it decreases if the diusivity is lower than in the parent phase. The most important contribution to solute drag comes from the spike of solute atoms in the parent phase being pushed forward by the advancing interface. The spike is thus an obstacle for growth that must be broken through in order for diusion-con-trolled growth to turn partitionless. The possibility of dynamic nucleation is also discussed. # 2000 Act