HIGH-TEMPERATURE CREEP-BEHAVIOR OF SINGLE-CRYSTAL OXIDES

The creep resistance of several single crystal oxides is evaluated on the basis of creep data from different sources using a Larson-Miller ( L-M) method. The possible creep mechanisms involved in high temperatur e creep deformation of single crystal oxides are discussed by comparin g the collected creep data with theoretical creep models. The high tem perature creep of single crystal oxides is generally considered as a d iffusion-controlled process: dislocation climb controlled by the latti ce diffusion of the slowest moving species (power law) at moderately h igh stresses, Harper-Dorn creep at low stresses, and power law breakdo wn at high stresses. The relative comparison of the creep data from di fferent sources using the L-M method and the general analysis about th e high temperature creep behaviour indicate that single crystal oxides with a precise stoichiometric composition, complex crystal structure and selected orientation such as [111] oriented YAG (Y3Al5O12), c-axis Al2O3, [110] oriented MgAl2O4 are potential candidates as reinforceme nts for very high temperature structural applications.