⁵⁹Fe Grain Boundary Diffusion in Nanostructured γ-Fe-Ni

Grain Boundary Diffusion in Metals: Recent Developments

“…The same feature was observed for Fe GB diffusion in nanocrystalline -Fe-40 mass%Ni. 39) The temperature dependence of Ni inter-agglomerate boundary diffusion D a is also presented in Fig. 18.…”

“…37) Recently, a new, more transparent classification was introduced which explicitely reflects the existence of two types of short-circuit diffusion paths in the material. [38][39][40] This classification refers to the microstructure which is presented in Fig. 13(a) and is sketched in Fig.…”

“…The difference between D gb and D a was explained by the relaxed state of the nanocrystalline GBs and a non-equilibrium character of the inter-agglomerate boundaries 39,40) resulting from the specific preparation method of the nanocrystalline -Fe-Ni alloy which allowed growth of the nano-grains from about 20 to about 100 nm of the grain diameter during the heat treatment of the powder sintered.…”

“…This microstructure was observed in the nanocrystalline -FeNi material produced by compacting and sintering the powders of Fe and Ni oxides. 39,41) The individual nano-scale grains (d ' 80{100 nm) are arranged in micrometer-size clusters or agglomerates (d a ' 30{50 mm). Accordingly, nanocrystalline GBs (intra-agglomerate boundaries) exist along with the inter-agglomerate boundaries.…”

“…(15)- (37), Ni and Fe diffusion in the two-scale nanocrystalline -Fe-Ni alloy was measured with the radiotracers 63 Ni and 59 Fe and subsequently analyzed. 39,40) In the case described, Ni diffusion along nanocrystalline GBs was measured in the C, B, and AB conditions, with the GB diffusivity D gb measured directly in the C and AB regimes and the product P ¼ Á D gb determined in the B regime. Summarizing all results derived in different regimes of GB diffusion and assuming ' 0:5 nm, the temperature dependence of the GB-diffusion coefficient D gb in the nanocrystals is plotted in Fig.…”