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

Flexural creep behavior of a Y-α-β sialon composite was studied in air at temperatures of 1250-1350°C and stresses of 110-290 MPa. The composite in which YAG was designed as intergranular phase has an original α/β ratio of 65/35. The stress exponents in Norton equation were determined to be 1.31±0.12, 1.49±0.15 and 1.62±0.10 at 1250, 1300 and 1350°C, respectively, and creep activation energy was 677±25 kJ mol^-1. Combining the microstructure observations, grain boundary diffusion accommodated by grain boundary sliding was identified as the rate-controlling creep mechanism for the composite. The creep rate exponent ρ in Monkman-Grant relation was found to be 1.6, and the nucleation and growth of cavities in triple grain pockets was responsible for the creep rupture.