PRESSURELESS SINTERING AND HIGH-TEMPERATURE STRENGTH OF SIC-AIN CERAMICS

Pressureless sintering of the SiC-AlN system with Y2O3 as a sintering aid was carried out. Composites with < 50 vol% SiC were densified to a bove 98% of the theoretical density in N2 atmosphere of 0.1 MPa at tem peratures below 1900-degrees-C using commercial SiC and AlN powders. T he densification behavior was investigated and analyzed on the basis o f microstructural observation. The strength and deformation of the den sely pressureless-sintered AlN and SiC-AlN composites were measured fr om room temperature to 1500-degrees-C by small punch testing. The sint ered AlN and SiC-AlN composites showed no strength decrease at tempera tures below 1200-degrees-C, whereas the SiC-AlN composites showed high er strength at room temperature and retained them to higher temperatur e. At 1500-degrees-C, plastic-like deformation was observed in the SiC -50 and 70 vol% AlN composites. The microstructural observation sugges ted that the fine microstructure with a uniform and fine grain size in the SiC-AlN composites was a dominant factor responsible for the plas tic-like deformation at high temperature.