An experimentally quantifiable solute drag factor

An empirically determined measure of the solute drag force called the drag factor is derived and defined. The drag factor is the derivative of mobility with respect to grain size, and describes well the drag effect of solute in the six different aluminas measured. A normalized drag factor allows direct comparison of different dopants, and validation of theoretically predicted trends. This construction is used to verify that the role of magnesia and rare-earth dopants in reducing the grain-growth rate is due to solute drag from the intrinsic mobility. These dopants segregate to the core of the grain-boundary, which differs from classical solute drag models that derive the drag effect from solute in the near-boundary lattice. The solute drag factor is also used to understand the role of drag in grain-boundaries that have mobilities that are enhanced relative to the pure material. This new approach for analyzing grain-growth advances the understanding of microstructural evolution and its relationship to properties.