Growth of intergranular creep cavities

Abstract

The current status of theory and experiment concerning the growth of intergranular cavities during high -temperature creep is reviewed. The proposed models for cavity growth are presented and their mathematical analysis is outlined. The predictions of these models are then compared. Experimental techniques for determining cavity growth rates or testing the predictions of the growth models (density, time to fracture, and metallographic measurements) are discussed. The results of recent experiments which purport to test cavity growth models are discussed in some detail and recommendations are made for further experiments. From the available evidence it would appear that all of the following modes of cavity growth can occur: (i) simple diffusional growth controlled by grain -boundary diffusion; (ii) deformation -enhanced diffusional growth; (iii) continuum plastic hole growth; (iv) crack -like diffusional growth controlled by surface diffusion; (v) unstable finger-like diffusional growth; and (vi) constrained diffusional growth. The relative ranges of operation of these mechanisms are indicated.