Effects of microstructure on the deformation mechanisms in silicon nitride

Changes in phase composition and morphology were investigated in silicon nitride (Si3N4) both before and after compressive deformation testing. Different additive systems were used to prepare Si3N4 specimens, resulting in either an initial α-phase or β-phase microstructure. Constant-strain-rate compression tests were used to evaluate the differences in the strain-rate dependency of the flow stress for the two phases. A flow-stress dependency of n = 1 was observed in the β-phase specimens, compared to an n value that approached 2 in the α-phase specimens.