AbstractÐDiusion induced grain boundary migration (DIGM) in the Cu(Zn) system was experimentally studied by Li and Hillert using polycrystalline Cu specimens zinci®ed with binary Cu±Zn alloys containing 3.9±30.5 wt% of Zn at temperatures between 573 and 773 K. Their experimental results have been quantitatively analyzed using the energy balance model proposed by Kajihara and Gust. The eective driving force D ef G for DIGM has been evaluated from the migration rate v of the moving boundary and the composition in the region alloyed with Zn behind the moving boundary, and then the mobility M of the moving boundary has been calculated using the relationship M vaÁ ef G. According to the analysis, the grain boundary migration obeys the chemical driving force model proposed by Hillert and Purdy for the largest experimental values of v at 573 and 623 K. However, the chemical driving force is partially consumed by the volume diusion of Zn in the Cu matrix ahead of the moving boundary for the other experimental values of v at 623±773 K. In such a case, the migration rate dependence of the eective driving force should be taken into consideration. The temperature dependence of the mobility gives a value of Q M 177 ktamol as the activation enthalpy for the grain boundary migration. This value is close to the activation enthalpy for volume diusion of Zn in Cu, 191 kJ/mol. Consequently, the grain boundary migration is considered to be controlled by the solute drag eect due to the volume diusion of Zn in the Cu matrix in the neighborhood of the moving boundary.