Evolution of vacancy densities in powder particles during mechanical milling

Abstract

This paper investigates the change in the density of vacancies during ball milling. A model for the evolution of vacancies has been proposed in this paper. Results from the simulation show that the density of vacancies increases asymptotically with collision times and the rate of increase becomes slower with further ball milling. The accumulation of vacancies in the powder particles is dramatically accelerated at lower milling temperature. Vacancies are shown to accumulate more easily in powder materials with higher vacancy migration energies. The present simulation indicates that higher collision frequency results in a faster accumulation of vacancies and therefore higher density of vacancies can 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 is too low. © 2002 Elsevier Science B.V. All rights reserved.