TY - JOUR
T1 - Structure models of massively transformed high niobium containing TiAl alloys
AU - Scheu, Christina
AU - Cha, Limei
AU - Sturm, Saso
AU - Chladil, Harald F.
AU - Mayrhofer, Paul H.
AU - Clemens, Helmut
AU - Wolf, Walter
AU - Podloucky, Raimund
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=34250875632&partnerID=8YFLogxK
M3 - 会议文章
AN - SCOPUS:34250875632
SN - 0272-9172
VL - 980
SP - 401
EP - 406
JO - Materials Research Society Symposium Proceedings
JF - Materials Research Society Symposium Proceedings
T2 - 2006 MRS Fall Meeting
Y2 - 27 November 2006 through 1 December 2006
ER -