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Structure Models of Massively Transformed High Niobium Containing TiAl Alloys

Published online by Cambridge University Press:  26 February 2011

Christina Scheu ,
Limei Cha ,
Saso Sturm ,
Harald F. Chladil ,
Paul H. Mayrhofer ,
Helmut Clemens ,
Walter Wolf  and
Raimund Podloucky
Christina Scheu
Affiliation:
[email protected], Montanuniversität Leoben, Department Physical Metallurgy and Materials Testing, Franz-Josef Strasse 18, Leoben, 8700, Austria
Limei Cha
Affiliation:
[email protected], Montanuniversität Leoben, Department of Physical Metallurgy and Materials Testing, Franz-Josef Strasse 18, Leoben, 8700, Austria
Saso Sturm
Affiliation:
[email protected], Jozef Stefan Institute,, Department for Nanostructured Materials, Ljubljana, N/A, Slovenia
Harald F. Chladil
Affiliation:
[email protected], Montanuniversität Leoben, Department of Physical Metallurgy and Materials Testing, Franz-Josef Strasse 18, Leoben, 8700, Austria
Paul H. Mayrhofer
Affiliation:
[email protected], Montanuniversität Leoben, Department of Physical Metallurgy and Materials Testing, Franz-Josef Strasse 18, Leoben, 8700, Austria
Helmut Clemens
Affiliation:
[email protected], Montanuniversität Leoben, Department of Physical Metallurgy and Materials Testing, Franz-Josef Strasse 18, Leoben, 8700, Austria
Walter Wolf
Affiliation:
[email protected], MaterialsDesign s.a.r.l, Le Mans, N/A, France
Raimund Podloucky
Affiliation:
[email protected], University of Vienna, Department of Physical Chemistry, Vienna, N/A, Austria
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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-46at.%Al-9at.%Nb in order to evaluate the effect of Nb on the crystal structure. The calculations revealed that upon doping with Nb the resulting structure can have Ti and Nb atoms on Al-sites, which leads to a reduction of the c/a ratio of the tetragonal γ TiAl cell to ~1.In contrast, the c/a ratio is increased, compared to the binary phase, if the Nb atoms occupy solely Ti sites and if Ti antisite defects (i.e. Ti 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.

Keywords

transmission electron microscopy (TEM)crystallographic structuresimulation
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 980: Symposium II – Advanced Intermetallic-Based Alloys , 2006 , 0980-II05-01
Copyright
Copyright © Materials Research Society 2007

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References

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