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Grain Boundary Self‐Diffusion in Polycrystalline Tungsten at Low Temperatures
Author(s) -
Lee J. S.,
Minkwitz C.,
Herzig Ch.
Publication year - 1997
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/1521-3951(199708)202:2<931::aid-pssb931>3.0.co;2-o
Subject(s) - tungsten , diffusion , grain boundary diffusion coefficient , materials science , grain boundary , atmospheric temperature range , effective diffusion coefficient , crystallite , enthalpy , thermal diffusivity , analytical chemistry (journal) , kinetic energy , self diffusion , thermodynamics , impurity , chemistry , metallurgy , microstructure , physics , medicine , organic chemistry , self service , business , radiology , chromatography , quantum mechanics , marketing , magnetic resonance imaging
Grain boundary (GB) self‐diffusion was investigated in sintered tungsten material by the radiotracer serial‐sectioning technique using the 185 W radioisotope. Measurements were carried out in the low‐temperature range from 1160 to 1323 K in the Harrison type‐C kinetic regime yielding directly the GB diffusion coefficient D GB = 1.41 × 10 —5 exp (—294 kJ mol —1 / RT ) m 2 s —1 . The activation enthalpy Q GB amounts to about 0.55 times the value Q V of W volume self‐diffusion. This ratio is larger than observed for GB diffusion in very pure metals ( Q GB ≈ 0.35 to 0.45 Q V ). From additional measurements at higher temperatures, 1873 to 2173 K, in type‐B kinetic regime, a smaller value of Q GB ≈ 0.45 Q V was estimated. By combining all results it is found that the GB diffusivity in the low‐temperature range is considerably reduced with respect to the extrapolated high‐temperature results. This observation is discussed in terms of a strong segregation effect of (spurious) impurities like C and P in the tungsten GBs.