Evaluation of densification mechanisms of liquid-phase sintering

Abstract

The contact flattening between grains has long been considered to be the densification mechanism during liquid-phase sintering. Recently, however, we proposed pore filling as being the major mechanism. In this investigation, we critically examine the two densification mechanisms by calculating their contributions to the sintering. The calculation shows that the contact flattening can be operative at the early stage for systems with a dihedral angle of zero degrees. However, its contribution to grain shape change and compact shrinkage is insignificant compared with that of the grain growth. A consideration of microstructures in real systems further suggests that the contribution of contact flattening is much less than the calculated value and is negligible from the beginning of the liquid-phase sintering. In fact, pore filling, which is induced by grain growth, appears to be essentially the only densification mechanism. An exemplified calculation of densification kinetics by pore filling is also presented and its implication discussed.