Development of Microstructure during Creep of Mullite and Mullite 5 vol SiC Nanocomposite

摘要

The microstructures of both mullite and mullite reinforced with 5 vol% nanosized SiC particles subjected to tensile creep have been investigated with TEM. The creep rates observed in the single-phase mullite were consistent with those in the literature where diffusional processes are reported and consistent with the low dislocation densities that were observed in the crept materials. Cavity formation at triple grain junctions in the mullite suggests that grain boundary sliding was also an active creep mechanism. Creep rates observed in the nanocomposite were lower than the rates predicted by diffusional processes for single-phase mullite of the same grain size. Particles were often observed near the cavities at multi-grain junctions indicating the importance of grain boundary pinning by intergranular particles, consistent with concepts based on interface controlled diffusional creep in particle hardened systems.