Inhibition of Void Dissolution by Vacancies

Dissolution of voids is a classical problem in the theory of sintering. The foundations of the theory were established by Frenkel, Pines and Geguzin (see Refs. 1 and 2 for a review). However, an important aspect of the problem appears to have been overlooked by previous workers. In a recent paper, the present authors identified a mechanism which inhibits processes associated with vacancy generation during grain growth, especially in fine grain sized materials [3]. The essence of the mechanism is the rise of the free energy of the system due to vacancy production in the course of defect ‘dissolution’ (decrease of the total area of grain boundaries) which under certain conditions may inhibit the rate of the primary process. A similar effect may also be operative in the case of void dissolution which is accompanied by a massive release of vacancies into the surrounding bulk of the material. In this paper we consider the conditions for intermittent temporary arrest of the void dissolution process leading to an effective decrease of the rate of dissolution.