Diffusion of Ag and Co in ultrafine-grained α-Ti deformed by equal channel angular pressing
Abstract
Grain boundary diffusion of Co and Ag was investigated in coarse-grained and ultrafine-grained (UFG) α-Ti. Ultrafine grained Ti was produced by equal channel angular pressing (ECAP) and diffusion measurements were performed in a temperature interval where no significant grain growth occurred. Grain boundary diffusion of Co was found to be 1-2 orders of magnitude slower in UFG Ti, despite the attendant activation enthalpy being similar to that in coarse-grained α-Ti. By contrast, grain boundary diffusion of Ag occurred at a significantly higher rate in the ECAP-modified UFG Ti. This behaviour is associated with the specific diffusion mechanisms of Ag and Co: while Ag diffuses preferentially via substitutional sites, diffusion of Co is dominated by interstitial jumps. The existence of so-called non-equilibrium interfaces in UFG Ti, providing an increased density of traps for the interstitially diffusing Co and simultaneously enhancing substitutionally diffusion of Ag, is confirmed by the diffusion measurements.
- Publication:
-
Journal of Applied Physics
- Pub Date:
- October 2011
- DOI:
- 10.1063/1.3650230
- Bibcode:
- 2011JAP...110h3514F
- Keywords:
-
- cobalt;
- deformation;
- enthalpy;
- grain boundary diffusion;
- grain growth;
- interstitials;
- pressing;
- silver;
- titanium;
- 66.30.J-;
- 61.72.jj;
- 65.40.G-;
- 81.40.Lm;
- 61.72.Mm;
- 62.20.F-;
- Diffusion of impurities;
- Interstitials;
- Other thermodynamical quantities;
- Deformation plasticity and creep;
- Grain and twin boundaries;
- Deformation and plasticity