DIFFUSION OF CR-51 ALONG HIGH-DIFFUSIVITY PATHS IN NI-FE ALLOYS

Penetration profiles of 51Cr in polycrystalline alloys Ni‐xFe (x = 0, 20, 40, and 60 wt.% Fe) after diffusion anneals at temperatures between 693 and 1473 K are studied. Sectioning of diffusion zones of samples annealed above 858 K is carried out by grinding, at lower temperatures by DC glow discharge sputtering. The concentration of 51Cr in depth x is assumed to be proportional to relative radioactivity of individual sections. With help of volume and pipe self‐diuffusion data taken from literature, the temperature dependence of product P = δDg (δ and Dg are grain boundary width and grain boundary diffusion coefficient, respectively) is obtained: P = (2.68 −0.88+1.3) × 10−11 exp { − (221.3 ± 3.0) kJ/mol/RT}m3/s. This result agrees well with the previous measurements of 51Cr diffusivity in Fe‐18 Cr‐12 Ni and Fe−21 Cr‐31 Ni. It indicates that the mean chemical composition of Fe‐Cr‐Ni ternary alloys is not a dominant factor affecting the grain boundary diffusivity of Cr in these alloys. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA