5. Diffusion and segregation at grain boundaries

The presence of a solute (an alloying element voluntarily added to a metal or alloy), or of an impurity, plays a major role in intergranular diffusion, whether of the solvent (or of a solvent) (self-diffusion) or of another solute (heterodiffusion), via the segregation factor $s$ . By performing a large number of diffusion experiments over a wide range of temperatures, we can determine the factor $s$ and the segregation energy of the diffusing solute. Intergranular diffusion is therefore a possible approach to equilibrium segregation.

In the case of a solid solution with infinite dilution and when the degree of segregation at the...