Solute drag, solute trapping and diffusional dissipation of Gibbs energy

There are several phenomena that depend on the interaction between solute atoms and migrating grain boundaries or phase interfaces. In order to explain them several models have been proposed and these are now reviewed. There are two approaches to this problem: the solute drag approach and the Gibbs energy dissipation approach. The latter has often been applied to a sharp interface model resulting in a treatment that is in accord with expectations from irreversible thermodynamics. When applied to the homogeneous interface model there are problems at high velocities. When applied to a wedge-shaped description of the properties of the interface, a very flexible treatment is obtained but it is difficult to decide how to choose the model parameters. The application of the solute drag approach to phase transformations is discussed. It is postulated that it should give the same result as the dissipation approach and this can be proved in simple cases. Applications to massive transformation, the effect of alloying elements on the formation of ferrite from austenite and DIGM are discussed. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd All Rights reserved.