It was noted that only 2 types of state were occupied in metal polycrystals during the intercrystalline diffusion of atomic probes. State-1 was localized in the grain-boundary core of metal polycrystals. State-2 was localized in lattice regions adjacent to grain boundaries. In 4d and 5d metals, 57Co atomic probes represented small-radius impurities and occupied interstitial sites in the grain boundary cores of these metals. In the case of 3d-metals, 57Co atomic probes were no longer small-radius impurities and therefore occupied only substitutional sites in the grain boundary core structure.

Equilibrium Sites Occupied in the Grain Boundary Core During Intercrystalline Diffusion of 57Co in Metal Polycrystals. V.N.Kaigorodov, S.M.Klotsman: Materials Science Forum, 1999, 294-296, 549-52. See also: Physics of Metals and Metallography, 1999, 87[5], 425-34