Self-diffusion and fast cobalt impurity diffusion in the bulk and in grain boundaries of hexagonal titanium
- 1 May 1991
- journal article
- research article
- Published by Taylor & Francis in Philosophical Magazine A
- Vol. 63 (5) , 949-958
- https://doi.org/10.1080/01418619108213927
Abstract
Bulk self-diffusion was measured in α-Ti single crystals between 776 and 1132 K using the radiotracer 44Ti and ion beam sputtering for profile sectioning. The results, which represent diffusion perpendicular to the c axis, follow a straight Arrhenius relation: Self-diffusion is interpreted by a vacancy mechanism. The low vacancy migration enthalpy may be related to the unusually low elastic constant c 66 in α-Ti. Grain-boundary self-diffusion was also measured in α-Ti; compared with corresponding results in other h.c.p. metals it was found to be in line with a vacancy mechanism. Grain-boundary diffusion of Co, which is a fast bulk diffuser, is six to seven orders of magnitude larger than grain-boundary self-diffusion. Even if a large Co grain-boundary segregation is accounted for, the evidence is that Co diffuses interstitially in α-Ti grain boundaries.Keywords
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