Creep cavitation without a vacancy flux

In a creeping solid holes may grow by vacancy condensation or by the action of the applied stress producing strains at the surface of the hole which cause it to grow. The latter mechanism does not involve a vacancy flux to the hole. A comparison of the two processes indicates the conditions under which hole growth without vacancy condensation is faster than hole growth by diffusion. Low values of the ratio σ/ε, where σ is stress and ε is the strain rate, as well as large voids favour the strain process. Such conditions usually arise in tertiary creep but may also occur earlier in the creep life. Experimental examples of cavitation in which vacancy condensation is shown to be the minor process are given, and the relevance of such a mechanism to hole growth in grain-boundary sliding and regions of localized flow is indicated.