Diffusion in mechanical alloying

Abstract

This paper studies the roles of two key factors in the mechanical alloying process, these factors being: activation energy, which is related to the formation of defects during the collision of powder particles; and crystalline size, which is related to the formation of nanometer crystalline during mechanical alloying. According to thermodynamic theory, the decrease in activation energy can result in an increase in diffusivity at constant temperature. Therefore, a decrease in activation energy is equivalent to an increase in temperature. High diffusivity can be obtained by creating a large number of defects through mechanical alloying. In addition, by creating nanometer size crystalline particles through the repeated fracturing and cold-welding of the powder particles, diffusion can take place easily through the grain boundaries. Consequently, elements which are difficult to diffuse may be alloyed using this technique. © 1997 Elsevier Science S.A.