Tensile behaviour of gas pressure sintered silicon nitride in the 1600–1700°C temperature range Original Research Article

The tensile behaviour of a silicon nitride ceramic has been studied between 1600 and 1680°C under strain rates from 6×10−6 to 1.2×10−5 s−1. At low temperature and/or high strain rate, the behaviour was essentially brittle: failure occurred by cavitation along boundaries of acicular grains lying normal to the tensile axis and linking of these cavities by interfacial debonding. At 1650°C, the deformation started to be ductile: a stress peak was observed in the tensile curve and cavities formed at multigrain junctions while grain boundary sliding began to occur. As the temperature increased, the contribution of grain boundary sliding to deformation increased at the expense of the cavitational component. The stress peak is interpreted in terms of a relaxation effect that governs the competition between cavitation and grain boundary sliding.