Deformation conditions for Ni powders undergoing mechanical processing

Ni powders were submitted to mechanical processing by ball milling. The microstructural refinement of the processed powders was followed by X-ray diffraction by evaluating the average crystallite size and the average strain content. The Vickers micro-hardness was also measured. The experimental evidences were rationalized using a phenomenological model, which allowed to estimate the amount of powder processed at individual collisions. The density of dislocations was also estimated and correlated with the experimental Vickers micro-hardness values. The connection between the work- and gain-hardening mechanisms described by the Bailey–Hirsch and Hall–Petch relationships is discussed.