A CONTINUUM MODEL FOR GRAIN JUNCTIONS IN POLYCRYSTALLINE AGGREGATE

Experimental results indicate that the material properties in the imme diate vicinity of the grain junction (GJ) differ substantially from th ose in the bulk material. It is assumed that the material in a vicinit y of GJ is in a specific state, somewhat amorphous, and that an interf ace exists between the vicinity and the bulk material. Employing Hsieh and Balluffi's (Hsieh, T.E., Balluffi, R.W., 1989. Acta Metall. 37,16 37) experimental data, the Laplace pressure at the interface is calcul ated. The stress field induced by the Laplace pressure at the interfac e between the GJ and bulk domains is considered. The stresses extend t he GJ domain and compress the grain material. In equilibrium, they dec rease as r(-2) for r --> infinity, where r is the distance from the ge ometrical center of the GJ to the point under consideration, and as r( -1) in the nonequilibrium case. The effect of grain anisotropy and tem perature changes on the generation of shear stresses at grain boundari es is discussed. The proposed model makes it possible to explain some phenomena specific to GJs from the unified standpoint. It should be he lpful for computational modeling. (C) 1998 Elsevier Science Ltd. All r ights reserved.