Pressureless Sintering and High-Temperature Strength of SiC-AlN Ceramics

Abstract

Pressureless sintering of the SiC-AlN system with Y2O3 as a sintering aid was carried out. Composites with<50vol% SiC were densified to above 98% of the theoretical density in N2 atmosphere of 0.1MPa at temperatures below 1900°C using commercial SiC and AlN powders. The densification behavior was investigated and analyzed on the basis of microstructural observation. The strength and deformation of the densely pressureless-sintered AlN and SiC-AlN composites were measured from room temperature to 1500°C by small punch testing. The sintered AlN and SiC-AlN composites showed no strength decrease at temperatures below 1200°C, whereas the SiC-AlN composites showed higher strength at room temperature and retained them to higher temperature. At 1500°C, plastic-like deformation was observed in the SiC-50 and 70vol% AlN composites. The microstructural observation suggested that the fine microstructure with a uniform and fine grain size in the SiC-AlN composites was a dominant factor responsible for the plastic-like deformation at high temperature.