Microstructure and creep behavior of a Y-α-β sialon composite

Four-point bending creep behaviour of a Y-α-β sialon composite with YAG as the intergranular phase and with the theoretical α/β ratio of 65/35 was studied at temperature 1250-1350°C and stresses of 110-290 MPa in air. The stress exponents at 1250, 1300 and 1350°C were found to be 1.31, 1.49 and 1.62, respectively, and creep activation energy was 677 kJ·mol^-1. Cavities were found mainly on multi grain junctions. Grain boundary diffusion coupled with sliding was identified to be the dominant creep deformation mechanism. The creep rate exponent, p, in Monkman-Grant relation was 1.6, and the nucleation/growth, coalescence and linkage of multi-grain-junction cavities were responsible for the creep rupture.