Columnar inter-grains and toughening of SiC-AlN ceramics induced by addition of alpha-SiC

The fabrication of SiC-AlN solid solutions with columnar inter-grains using the addition of small amounts of alpha-SiC to an AlN-beta-SiC mix was stud ied by hot-pressing under 2030 degrees C. The appreciable amounts of alpha- SiC content for a reaction of AlN and beta-SiC affected the SiC-AlN phase r elationships and the microstructures by stabilizing a 2H phase. It could de velop columnar inter-grains of 4H phase and the stable 2H phase with a unif orm composition and grain size distributions. The alpha-SiC containing samp les showed fracture toughness of 5.1-5.4 MPa m(1/2). The fracture toughness was related to the amounts of 4H present. The enhanced fracture toughness was due to the reinforcement of the columnar inter-grains of 4H phase in th e 2H phase induced by appreciable amounts of alpha-SiC. (C) 2000 Elsevier S cience B.V. All rights reserved.