Creep Strain Due to Stress-Enhanced Sintering of Intergranular Cavities

Abstract

Creep can occur by dislocation movement, grain-boundary sliding, or diffusion of vacancies from grain-boundary sources to grain-boundary sinks. Another mechanism has recently been proposed whereby a diffusional creep-strain component can arise due to the growth of cavities situated on grain boundaries normal to the tensile stress axis. It is implicit in this model that a diffusional creep component should also occur in materials containing existing cavities when tested in compression. Here experimental evidence is presented obtained on uranium dioxide which supports this view. Comparisons are made between experiment and theory, limitations of the theory are discussed and a modification is made to take account of a distribution of cavity sizes.