The Diffusional Creep Strain Due to the Growth of Intergranular Voids

Abstract

During creep deformation of metals at high temperatures the failure process often consists of the nucleation and growth of voids on those grain boundaries that are normal to the stress axis. Where void growth results from the transference of vacancies from the grain boundary to the void the process is equivalent to the plating out of atoms along the boundary, thereby achieving creep strain in a direction parallel to the stress axis. Theoretical strain/time curves have been derived and it is suggested that this straining process may be particularly important in lightly stressed engineering components with long design lifetimes. During the fracturing process the stress across the normal grain boundary rises as the load-bearing area decreased. It is shown that neglect of this feature leads to an appreciable error in estimates of the time to failure.