CHEMICAL STRESSES INDUCED BY GRAIN-BOUNDARY DIFFUSION

Based on Whipple-Suzuoka solutions, the chemical stresses induced by g rain-boundary diffusion under constant- and instantaneous-source conce ntrations are investigated. For a finite boundary, the chemical stress consists of both compression and tension fields, in the sequence of c ompression I-tension-compression II, with the compression I field near the diffusion interface. The magnitudes and distributions of these fi elds differ for different source concentrations and are strongly affec ted by the ratio of diffusivity in the grain boundary and diffusivity in the lattice (D'/D). As D'/D increases, the magnitude of the compres sion I field decreases and that of the tension and compression II fiel ds increases. An increase in D'/D also increases the range of the comp ression I field. The trend is distinct in the case of constant-source diffusion, while in the case of instantaneous source diffusion, both t he tension and compression II fields appear to be extremely small.