A new approach to solute effect on grain boundary migration

Solute drag theory is revisited and an alternative approach is presented to account for the effect of solute elements on grain boundary migration during annealing. A fundamental new concept is introduced in the model that, in the linear range of irreversible thermodynamics, solute atoms segregated in a grain boundary will not lag behind when the boundary migrates. While lagging behind is the very essential assumption for the solute drag theory the mobility drop due to solute addition is attributed to the decrease in boundary energy as a result of boundary segregation instead of blaming the lagging behind. According to this model, grain boundary mobility is dependent on solute concentration rather than migration rate. The predictions of the model are in qualitative agreement with experimental results.