Abstract
The effect of the average particle size or specific surface area on the expansion phenomenon observed in vacuum-sintering high density Cu powder compact without lubricant was investigated and mechanisms proposed so far for the expansion phenomenon were reconsidered.
The results obtained are as follows; (1) The critical relative density of green compact, i.e., the density above which the compact expands due to sintering, largely depended on the average particle size or specific surface area; It decreased with decreasing particle size or increasing specific surface area. (2) Among so far proposed mechanisms, both residual stress(or strain) and entrapped air in the compact were made clearl to have minor effects on the expansion. (3) The expansion was considered to be generally caused by CO2 and H2O gases evolved from the powder. The source of these gases was discussed in some detail.
