Diffusion

· The voids between powder particles are removed by material transfer to the "neck" between them. This decreases the surface-to-volume ratio and the curvature in the neck region both of which reduce the Gibbs function of the system.

From: Edwards & Endean, "Manufacturing with Materials," Butterworths (1990)

· The transport paths involved in generating a "neck" region between particles are shown above. Surface diffusion, boundary diffusion, diffusion along dislocation cores, and bulk diffusion, contribute to material transport to the neck. Vapor phase transport can also occur.