Crystallite size refinement in elemental species under mechanical processing conditions

A systematic study of the crystallite size refinement process of elemental species under mechanical processing conditions has been carried out. Elemental powders were treated in a milling device at different intensities. The dependence of the rate of size reduction as well as of the final crystallite size attained on both impact energy and collision frequency was thus investigated. The final crystallite size shows only a weak dependence on the average impact energy. Conversely, the latter greatly affects the rate of crystallite size decrease. A threshold impact energy is also observed below which no significant structural refinement occurs. The threshold energy is found to scale with the shear modulus of the chemical species.