The simple model of grain and phase boundaries diffusion into polycrystalline solid system with micro grain dimensions is proposed. There are considered different types of diffusion regimes which are realized by definite correlations between volume and grain boundary diffusion lengths and average grain sizes.
Grain boundary wetting process takes place during the contact of solid metal phase with the metal melt. The liquid bismuth network formation along grain boundaries (GB) connected with wetting process was investigated in copper polycrystalline samples. The endothermic thermal effect in the temperature range close to complete GBs wetting transition temperature for Cu-Bi system was observed. Thermal effect size of GB wetting per mol of copper passed into bismuth melt during process of forming wetting GB channels was characterized as 21-23 kJ/mol.