Diffusion and the Isotope Effect for Diffusion of Homovalent Impurities - Molybdenum and Chromium - in Tungsten Single Crystals

The Structural Evolution and Densification Mechanisms of Nanophase Separation Sintering

“…The activation energy of grain boundary diffusion is approximately half of the bulk diffusion activation energy for Cr in W (547 kJ/mol) and the diffusion prefactor for a bcc metal is 1.8 × 10 −5 𝑚 2 /𝑠. For bulk diffusion of Cr in W, the diffusion prefactor is 8.5 × 10 −5 𝑚 2 /𝑠 [40] .Using these parameter Eq. ( 5) gives a ratio of ~10 5 ; diffusion covers many thousands of times more distance along grain boundaries than in the bulk at these times/temperatures.…”