Creep Mechanisms in Multiphase Ceramic Materials

Hard, refractory particles long have been added to ceramic materials to impart creep resistance. The nature of such particles and the volume fraction added may vary widely between different systems. As a result, a rich variety of creep behavior and of attendant mechanisms is found. A critical survey is presented of the experimental data and of the models developed to rationalize them. Particular attention is paid to three materials systems: whisker‐reinforced ceramics (e.g., SiC‐whisker‐reinforced Al 2 O 3 ); infiltrated powder compacts (e.g., siliconized SiC); and glass‐bonded ceramics (e.g., sintered Si 3 N 4 ). A microstructural classification system is presented based on the nature of the network developed by the hard particles. This is useful as a guideline in developing mechanistic models. The current state of such models is reviewed critically. Although models for the high‐ and low‐volume‐fraction regions are well advanced, those applicable at intermediate volume fractions—relevant to whisker reinforcement for example—remain at an early stage. Finally, the experimental data on a range of materials are reviewed and classified. These data are compared with the models.