GRAIN-BOUNDARY DIFFUSION OF CO-60 IN NICKEL

The grain boundary heterodiffusion of Co‐60 in Marz‐nickel polycrystals is investigted in the range from 673 to 1323 K by means of the serial sectioning method. It is shown that the temperature dependence of the triple product P = sδDg (s, δ, and Dg stand for segregation factor, grain boundary width, and grain boundary diffusion coefficient, respectively) is of the Arrhenius type, but is characterized by two different activation enthalpies. The values of pre‐exponential factor sδDgo and activation enthalpy Hg for the high temperature region (from 933 to 1323 K) are (5.1 −3.2+9) × 10−15 m3/s and (120 ± 6) kJ/mol, respectively. In this temperature interval the grain boundary diffusion characteristics for Co‐60 lie lower than those published for the self‐diffusion in Ni. However, at lower temperatures (between 673 and 803 K) the products P lie close to self‐diffusion characteristics and the corresponding Arrhenius parameters are (1.3 −0.56+1.6) × 10−11 m3/s and (174 ± 7) kJ/mol. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA