Abstract
The effects of particle size on the void volume of green and sintered compacts have been studied with tungsten powders from 2.9 to 0.022μ in average diameter.
The void volume of green compacts increased with decreasing particle size down to 0.3μ, but it remained essentially constant with further decrease in particle size.
The sintering process of 0.022μ-powder consists of three stages. The first stage is characterized by an activation energy of 79 Kcal/mole and the surface diffusion mechanism would be operative. The activation energies of the second and the third stage are 102 and 124 Kcal/ mole respectively, the latter is comparable to that expected in volume diffusion. In the sintering of 0.022-powder, the first stage is important and 50-60% reduction in void volume was recorded. On the other hand, for coarser powders 60-80% reduction in void volume was observed after the second stage.
