Mechanisms of Creep Resistance of Advanced Directionally Solidified Eutectics: Experiments and Modeling

摘要

The creep resistance of the directionally solidified ceramic eutectics of alumina/cubic zirconia was studied experimentally in the 1200-1520 C, and 100-275 Mpa stress range, with associated TEM and SEM microscopy, as a generic example of ceramic eutectics. Additional computer simulations were done both at the atomic level and by FEM methods to study: (a) the core structure of pyramidal edge dislocations in alumina that can only climb but not glide; and (b) the stress distribution in the alumina component during creep. A creep model based on diffusional climb of pyramidal system edge dislocations was in very good agreement with the measured creep rates. The model predicts that the creep resistance of the eutectics should be superior to that of pure sapphire fiber in the above temperature range, and must be considered as potential candidates for high temperature structural applications. Exploitation of their full potential in high temperature composites, however, requires extensive engineering materials development.