This paper investigates the change in the density of vacancies during ball milling. A model for the evolution of vacancies was proposed in this paper. Results from the simulation showed that the density of vacancies increased asymptotically with collision times and the rate of increase became slower with further ball milling. The accumulation of vacancies in the powder particles was dramatically accelerated at lower milling temperature. Vacancies were shown to accumulate more easily in powder materials with higher vacancy migration energies. The present simulation indicated that higher collision frequency results in a faster accumulation of vacancies and therefore higher density of vacancies could be obtained. In addition, higher impact energy introduces higher density of vacancies per collision. Low milling temperature, high collision frequency and high collision energy may be advantage for the formation of new alloys, but low migration rate of vacancies at low temperature may reduce the rate of the formation of new alloys if the milling temperature was too low.

Evolution of Vacancy Densities in Powder Particles during Mechanical Milling. B.Q.Zhang, L.Lu, M.O.Lai: Physica B, 2003, 325, 120-9