Ultrahigh-temperature deformation of high-purity HIPed Si3N4

High-temperature tensile deformation behavior of high-purity HIPed silicon nitride material was investigated in the temperature range between 1600 deg reesC and 1750 degreesC. Recoverable anelastic and non-recoverable deformat ion was observed in high-purity HIPed silicon nitride. A power-law deformat ion model analogous to rheological models was used to distinguish the diffe rent deformation components. A stress exponent n = 1.64 and an activation e nergy Q(1) = 708 kJ/mol was determined for the non-recoverable deformation. For the anelastic deformation a stress exponent p = 4 and an activation en ergy Q(3) = 619 kJ/mol was observed. Diffusional creep and grain boundary s liding with the accomodation process responsible for the anelastic componen t are discussed as deformation mechanisms. (C) 2001 Kluwer Academic Publish ers.