Diffusion

· Not all powders are spherical in form, but processes similar to those discussed control sintering and pore removal.
· The photograph shows the microstructure of an iron-copper-carbon alloy. The iron, carbon, and copper powders are mixed in the correct ratio for alloy formation.

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

· Cold pressing bonds the system mechanically. On sintering, the alloying process proceeds by copper and carbon diffusion into the iron particles. Selecting an alloy with 3 weight % copper in iron ensures that little volume change occurs and that 95% of theoretical density is reached after sintering.