The growth of creep cavities by grain boundary sliding

Abstract

Using an energy balance argument it is shown that cavity grwoth is a 2-stage process. During Stage I the cavity behaves as a shear crack whose rate of increase of length is equal to the grain boundary sliding rate. The relationship is not affected by the direction or magnitude of the normal applied stress. In Stage II the growth rate continuously accelerates and final fracture can occur in a Griffith-Orowan type manner. The analysis is applied successfully to a number of experimental observations which include the kinetics of density change during creep and the inhibiting effect of a hydrostatic pressure.