DENSIFICATION AND SINTERING KINETICS OF RARE-EARTH (ALPHA'-SIALON COMPOSITES(BETA'))

The sintering processes of Re-(alpha' + beta')-sialon composites (Re=S m, Dy, Yb) have been investigated by using a specially designed high t emperature dilatometer. The initial densification of various samples s tarts at about 1200 degrees C, and the maximum shrinkage rate of these sialon composites occurs at about 1500 degrees C. The light rare eart h sialon has a noticeably lower densification temperature and a higher final shrinkage. The sintering kinetics of Re-(alpha' + beta')-sialon are much more complex. The Kingery's liquid phase sintering model app ears to be applicable, but :he mechanism of mass transport in stage tw o appears to be changeable. The controlling factor shifts from solutio n-precipitation to diffusion when densification process proceeds from the earlier part to the later part of this stage.