Segregation of ~(57)Co Atomic Probes in the Cores of Grain Boundaries in d-Transition Metals

摘要

A new method, which has been developed to examine the structure and physical properties of cores of grain boundaries (GB's) (S.M.Klotsman, Sov. Phys. Uspech. 33, 55 (1990); V. N. Kaigorodov and S. M. Klotsman, Phys. Rev. B 49 (1994)), was used to study segregats localized in two discrete regions of polycrystals: cores of GB's and two-dimensional regions of the lattice adjacent to the GB's. This paper reports and discusses results of investigations of segregation of ~(57)Co atomic probes in cores of GB's in the d-transition metals Cr, Ta and W. The interaction of ~(57)Co AP's with GB's cores in metals is similar to their interaction with vacancies, because GB's cores are characterized, as vacancies in metals, by an excess volume and a negative charge. GB's are enriched with ~(57)Co in chromium and tungsten. The activation enthalpy of the ~(57)Co atomic probes segregation at GB's in Cr and W is proportional to the local magnetic moment of ~(57)Co atomic probes. GB's cores are found to be depleted of ~(57)Co atomic probes in Ta.