The effect of triple-junction drag on grain growth

Current theories of grain growth presume that grain boundary migration is t he rate-limiting step, and either explicitly or implicitly assume that trip le junctions can always move with sufficient speed to accommodate the chang ing positions of the grain boundaries. Following from some recent observati ons of triple-junction drag effects in tricrystals of zinc and in molecular dynamics models, an analytical theory is developed to explore the effects of triple-junction drag upon grain growth, for a two-dimensional solid. The theory is developed in the framework of the Von Neumann-Mullins formulatio n, and demonstrates that drag effects operating exclusively at the triple j unctions result in a retardation of grain growth. The stability of six-side d grains in the isotropic, drag-free case of the Von Neumann-Mullins analys is is successively extended to grains of 6 +/- N sides, where N increases w ith the strength of the triple-junction drag. (C) 2000 Acta Metallurgica In c. Published by Elsevier Science Ltd. All rights reserved.