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 (α-Ti, α-Zr, and α-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 hop 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 ≈ 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 α 2-Ti3Al are reviewed. Interphase boundary diffusion of Ti in the unidirectional lamellar α 2/ γ structure of the two-phase Ti48Al52 alloy is analyzed with respect to the phase boundary structure and GB self-diffusion in α 2-Ti3Al.
- Publication:
-
Metallurgical and Materials Transactions A
- Pub Date:
- March 2002
- DOI:
- 10.1007/s11661-002-1006-4
- Bibcode:
- 2002MMTA...33..765H