Bulk and interface boundary diffusion in group IV hexagonal close-packed metals and alloys

Abstract

Bulk and grain boundary (GB) self-diffusion and substitutional solute diffusion in group IV hexagonal close-packed (hcp) metals (␣ -Ti, ␣ -Zr, and ␣ -Hf) are reviewed. The recent results obtained on high-purity materials are shown to approach closely the "intrinsic" diffusion characteristics. The enhancement effect of fast-diffusing impurities (such as Fe, Ni, or Co) is discussed for both self-and substitutional bulk solute diffusion in terms of the interstitial solubility of the impurity atoms. In GB self-diffusion, the impurity effect is found to be less dramatic. The results obtained on high-purity hcp materials can be interpreted in terms of intrinsically 'normal' vacancy-mediated GB diffusion, with the ratio of GB to volume diffusion activation enthalpies of Q gb /Q Ϸ 0.6. The GB self-diffusion in group IV hcp metals reveals distinct systematics. Bulk self-diffusion and fast interstitial solute diffusion (Fe and Ni) in the hcp phase ␣ 2 -Ti 3 Al are reviewed. Interphase boundary diffusion of Ti in the unidirectional lamellar ␣ 2 /␥ structure of the two-phase Ti 48 Al 52 alloy is analyzed with respect to the phase boundary structure and GB self-diffusion in ␣ 2 -Ti 3 Al.

Recoil Induced Room Temperature Stable Frenkel Pairs in a-Hafnium Upon Thermal Neutron Capture

“…Incidentally, it was purchased from the same company [9] as that used for self-diffusion studies by Herzig et al [13] who quote a zirconium concentration of 129 wt/ppm and further impurities at much lower levels. Although our sample is very likely from a different batch, we believe that rather similar impurity levels also apply to our sample.…”

Self-diffusion in the hexagonal structure of Zirconium and Hafnium: computer simulation studies

“…Regarding self-diffusion behavior, the studies in α-Hf demonstrate generally a good linearity of the Arrhenius plot, and only at the lowest temperature a slight upward deviation can be supposed 1 . Also α-Ti, contrary to α-Zr, shows an Arrhenius behavior independently of the impurity content [1][2] . According to Herzig et al…”

“…Herzig et al 1 and Pérez et al Pérez et al 2 support the fact that small metallic atoms, such as Fe, Cr or Ni, act as fast-diffusing impurities and produce a pronounced enhancement effect on both self-and substitutional bulk solute diffusion in these metals. Regarding self-diffusion behavior, the studies in α-Hf demonstrate generally a good linearity of the Arrhenius plot, and only at the lowest temperature a slight upward deviation can be supposed 1 .…”

“…A detailed revision on bulk and interface boundary diffusion in group IV hexagonal close packed (hcp) metals (Ti, Zr and Hf) and alloys has been recently carried out by Herzig et al 1 . Also, an overview on self-and impurity diffusion in hcp Ti and Zr, due to Pérez et al, is found in quotation 2 .…”

Модель зернограничной самодиффузии в alpha- и beta-фазах титана и циркония

“…Диффузионные свойства титана и циркония достаточно хорошо экспериментально изу-чены [6][7][8][9][10], однако до сих пор в их теоретическом описании остаются пробелы.…”