KINETICS OF MICROSTRUCTURE EVOLUTION IN NANOCRYSTALLINE Fe POWDER DURING MECHANICAL ATTRITION

摘要

The microstructure evolution in Fe powder during ball milling at different temperatures and intensities is investigated. Steady-state grain sizes below l2 nm are obtained, which increase weakly with decreasing milling intensity or increasing temperature. A phenomenological model is proposed, based on the assumption of simultaneous grain refinement and grain growth. This model fits well all data sets. The weak temperature dependence of the grain-growth term is consistent with nonequilibrium vacancy pro- duction. The fit results indicate that the efficiency for refinement and vacancy production decreases with increasing vibration amplitude.