Anomalously linear grain growth in nanocrystalline Fe

Isothermal grain growth curves recorded in nanocrystalline Fe at 423 and 452 °C manifest a linear time dependence followed by an equally anomalous acceleration in growth rate, accompanied by a broadening and then a narrowing of the grain-size distribution. This behavior appears not to result from a transition in the rate-controlling mechanism for grain growth from triple-junction to grain-boundary migration, as posited previously. Rather, the observations are found to be consistent with the predictions of a phenomenological model for abnormal grain growth.