Densification mechanisms in spark plasma sintering: Effect of particle size and pressure

Three particles size ranges (< 25, 25–45 and 45–90 μm) of a commercial as-atomized copper powder were used to study the effect on SPS mechanism of particle size, pressure and the temperature at which pressure is applied. Under the application of a low initial pressure, densification is due to: particle rearrangement, localized deformation, bulk deformation and neck growth. The first two mechanisms are enhanced by an increase in particle size. Bulk deformation is not affected and neck growth is instead enhanced by a decrease in particle size. If pressure is increased during the SPS cycle, temperature at which it is applied does not influence sintered density significantly, but tensile ductility, which is significant of the effectiveness of sintering, increases if pressure is applied either during or after the bulk densification.