Effect of the intergranular glass composition on high temperature compressive deformation of silicon nitride

Abstract

The effect of chemical composition of Y₂O₃-MgO-SiO₂-based intergranular glass on high temperature deformation of alpha-Si₃N₄ was studied by compression tests at elevated temperatures. All spark plasma sintered Si₃N₄ had the same initial microstructures and the same amount of glass phase, which was different in composition only. The flow stress was not proportional to the original viscosity of Y₂O₃-MgO-SiO₂ glass, probably, because the chemical composition of the glass changed during sintering. The difference in the chemical composition of glass altered the microstructural evolution at elevated temperatures, thus, peculiar stress-strain curves were observed in the deformation tests.