The Formation and Growth of Cavities in Creep

AbstractGrain-boundary dislocations may play a crucial role in creep fracture.Despite initial successes, the existing diffusion theory regarding the formation and growth of cavities in creep is now encountering serious difficulties in its attempt to deal with the rates of these processes. For instance, the measured growth rates of cavities have been found to agree with those calculated from the diffusion theory in the case of a pure metal; in the case of a strong alloy the calculated rate would not alter much, since diffusion coefficients are not changed substantially by alloying, but the actual rate is greatly reduced in something like the same ratio as the creep rate. Theory and experiment are then far apart. Another instance is that in an early calculation in which the competition between the opening of a cavity by grain-boundary sliding and its closure by sintering was considered, it was concluded that the latter did not predominate over the former, but correction of an error reverses this conclusion....