E. L. Dreizin, P. R. Santhanam
Discrete element model (DEM) is used to describe energy transfer from milling tools to the milled powder for shaker, planetary, and attritor mills. The rolling and static friction coefficients are determined experimentally. Computations predict the quasi-steady rate of energy dissipation, Ed, for each experimental configuration. It is proposed that the milling dose defined as a product of Ed and milling time, t, divided by the mass of milled powder, mp characterizes the milling progress independently of the milling device or milling conditions used. Once milling dose is determined for one experimental configuration, it can be used to predict the milling time required to prepare the same material in any milling configuration, for which Ed is calculated. To validate this concept, metal-oxide composites were prepared using all three types of mills. The yield strength of the milled material was used as an experimental indicator of the milling progress. The concept was validated for DEM describing both planetary and shaker mills. For attritor, the predicted energy dissipation includes substantial contribution from the milling tool interaction events accompanied by abnormally high forces (> 103 N). Because of high forces, the energy in such events is likely dissipated to heat or plastically deform milling tools rather than refine material. Indeed, DEM predictions for attritor correlate with experiments when such events are ignored in the energy dissipation analysis.
Computer simulation, Mechanical alloying, Mechanical milling, Nanocomposite, Reactive milling