Diffusion of Iron in β-Titanium under Hydrostatic High Pressure

抄録

The impurity diffusion coefficient of Fe in β-Ti has been determined at temperatures of 1223 and 1273 K under pressures of 0. 1 MPa to 3. 0 GPa using (Ti) - (Ti-1. 93 at%Fe) diffusion couples. The diffusion coefficient decreases with pressure, and the values of activation volume, ΔV, are 0. 27Ω at 1223 K and 0. 23Ω at 1273 K, where Ω is the atomic volume of the host metal. The results of the present work contradict previous reports of negative activation volumes for Fe diffusion in the β-phase of Ti and Ti-4 at%Fe alloy, whereas are in good agreement with the recent study for the fast diffusion of Co and Ni in β-Ti. The magnitudes of ΔV/Ω obtained in the present work, which are approximately half of that normally expected for diffusion in bcc metals via monovacancy mechanism, can be interpreted in terms of the interstitial-substitutional dissociative model.