Bulk and grain-boundary self-diffusion and substitutional solute diffusion in group-IV hexagonal close-packed metals were reviewed. Recent results on high-purity materials were shown to approach closely the so-called intrinsic diffusion characteristics. The enhancement effect of fast-diffusing impurities (Fe, Ni, Co) was considered, for both self- and substitutional bulk solute diffusion, in terms of the interstitial solubility of the impurity atoms. In the case of grain-boundary self-diffusion, the impurity effect was found to be less marked. The results which were obtained by using high-purity hexagonal close-packed materials could be interpreted in terms of so-called normal vacancy-mediated grain-boundary diffusion; with a ratio, of grain boundary to volume diffusion activation enthalpy, of 0.6.

Bulk and Interface Boundary Diffusion in Group-IV Hexagonal Close-Packed Metals and Alloys. C.Herzig, Y.Mishin, S.Divinski: Metallurgical and Materials Transactions A, 2002, 32[3A], 765-75