Pores are formed in compaction process of green compacts, and then coalesce or shrink in sintering. Pores are main characteristics of PM (powder metallurgy) alloy parts. These parts gain certain kind of properties due to the presence of pores inside. Thus, materialists are trying to control the shape, the size and the distribution of pores in the PM parts.
Green compacts are usually compacted from multiple powders, which include both hard particles to construct the skeleton and soft particles to bind the skeleton. In the cold compaction of the multiple powders mixture, the pore size in the green compacts is mainly affected by the size and the shape of the hard particles in these powder mixtures.