Abstract
Ab-initio calculations using the Vienna ab-initio simulation package (VASP) were performed for a high Nb bearing γ-TiAl based alloy with a composition of Ti-47at.%Al-9at.%Nb in order to evaluate the effect of Nb on the crystal structure. The calculations revealed that the c/a ratio of the tetragonal γ-TiAl cell is reduced to ∼1, compared to the binary phase, if Nb atoms occupy Ti- and Al sites. In contrast, the c/a ratio is increased, in comparison to the pure γ-TiAl, if the Nb atoms occupy solely Ti sites and if Ti antisite defects (i.e. Ti atoms on the Al sublattice) are formed. The relaxed structure models were used to perform high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image simulations. The results showed that the positions of the Nb atoms should be detectable by these high spatial resolution methods, although it might be easier by HAADF-STEM investigations due to the stronger dependence of the signal on the atomic number Z.
| Original language | English |
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| Pages (from-to) | 401-406 |
| Number of pages | 6 |
| Journal | Materials Research Society Symposium Proceedings |
| Volume | 980 |
| State | Published - 2007 |
| Externally published | Yes |
| Event | 2006 MRS Fall Meeting - Boston, MA, United States Duration: 27 Nov 2006 → 1 Dec 2006 |