Abstract
Mechanical alloying process, especially conducted by ball milling of metal powders, shows poor reproducibility, since we have few indices adequate for the mathematical description of the process. Energy consumption by the plastic deformation of metal powder particles in the mechanical alloying process can be a good index for the mathematical description. However, it is much difficult to measure the energy consumption only by the plastic deformation of metal powder particles. In this study, the authors tried to trace the motion of individual milling balls in a tumbling ball mill during ball milling of a metal powder, by using a three-dimensional model simulation based on discrete element method. From the motion of individual balls calculated by the simulation, frequency of collision event as well as distribution of impact velocity were estimated as a function of ball filling ratio, J. As a result, the motion of balls and therefore the distribution of impact velocity were affected signifficantly by the ball filling ratio. Especially, the frequency of collision event having higher impact velocities shows an maximum at J=0.5. This means that the plastic deformation of the metal particles is most promoted at J=0.5 if the plastic deformation requires higher impact velocity.
