High carbon solubility in a γ-TiAl-based Ti–45Al–5Nb–0.5C alloy and its effect on hardening
✍ Scribed by C. Scheu; E. Stergar; M. Schober; L. Cha; H. Clemens; A. Bartels; F.-P. Schimansky; A. Cerezo
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 446 KB
- Volume
- 57
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
The C distribution within the c-TiAl-phase of a Ti-45Al-5Nb-0.5C alloy with near-c microstructure was studied by atom probe tomography. In most areas, the C atoms were homogeneously distributed, and only a few C-enriched features were detected, which were presumably Cottrell atmospheres surrounding dislocation cores. The C concentration within the c-phase was measured to be $0.25 at.%, which is a factor of 10 higher than the solubility limit reported for other TiAl alloys. The reason for this unusually high C solubility is explained by an existing model, which relates the number of octahedral sites consisting of six Ti atoms to the solubility limit of interstitials. The large amount of C in solid solution can explain the results of a recent study which showed that the C-containing alloy had a $30% increase in yield strength compared with a C-free sheet containing the same Ti, Al and Nb concentrations.