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°C and 1750°C. Recoverable anelastic and non-recoverable deformation was observed in high-purity HIPed silicon nitride. A power-law deformation model analogous to rheological models was used to distinguish the different deformation components. A stress exponent n = 1.64 and an activation energy Q ₁ = 708 kJ/mol was determined for the non-recoverable deformation. For the anelastic deformation a stress exponent p = 4 and an activation energy Q ₃ = 619 kJ/mol was observed. Diffusional creep and grain boundary sliding with the accomodation process responsible for the anelastic component are discussed as deformation mechanisms.