A continuum model for grain junctions in polycrystalline aggregate

Experimental results indicate that the material properties in the immediate vicinity of the grain junction (GJ) differ substantially from those in the bulk material. It is assumed that the material in a vicinity of GJ is in a specific state, somewhat amorphous, and that an interface exists between the vicinity and the bulk material. Employing Hsieh and Balluffi's (Hsieh, T.E., Balluffi, R.W., 1989. Acta Metall. 37,1637) experimental data, the Laplace pressure at the interface is calculated. The stress field induced by the Laplace pressure at the interface between the GJ and bulk domains is considered. The stresses extend the GJ domain and compress the grain material. In equilibrium, they decrease as r^-2 for r → ∞, where r is the distance from the geometrical center of the GJ to the point under consideration, and as r^-1 in the nonequilibrium case. The effect of grain anisotropy and temperature changes on the generation of shear stresses at grain boundaries is discussed. The proposed model makes it possible to explain some phenomena specific to GJs from the unified standpoint. It should be helpful for computational modeling.