The low-temperature portion of the Arrhenius plot for the occupancies of states in the intercrystalline diffusion zone of 57Co in polycrystalline W was analyzed. It was shown that the concentration of free vacancies, which were present in the segregation zone due to the thermal decomposition of vacancy-impurity complexes, was sufficiently high to provide a high diffusivity of 57Co in this zone; even at homologous temperatures as low as 0.18. A temperature range was found within which the occupancies of states varied due to the temperature dependence of the segregation coefficient for 57Co atomic probes. The activation enthalpy for such segregation was 20W/mol, and the relative width of the region steadily enriched in point defects, where the pumping coefficient of 57Co from the core of crystallite-conjugation regions was much larger than the coefficient of bulk diffusion, was determined from experimental data.

Intercrystalline Diffusion of Cobalt in Polycrystalline Tungsten III. Pumping Mechanism of Substitutional Atomic Probes at Low Temperatures. S.M.Klotsman, V.N.Kaigorodov, M.I.Kurkin, V.V.Dyakin: Physics of Metals and Metallography, 1998, 85[3], 342-7