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Massive Transformation in High Niobium Containing TiAl-Alloys

Published online by Cambridge University Press:  26 February 2011

A. Bartels ,
S. Bystrzanowski ,
H. Chladil ,
H. Leitner ,
H. Clemens ,
R. Gerling  and
F.-P. Schimansky
A. Bartels
Affiliation:
Materials Science and Technology, TU Hamburg-Harburg, D-21073 Hamburg, Germany
S. Bystrzanowski
Affiliation:
Materials Science and Technology, TU Hamburg-Harburg, D-21073 Hamburg, Germany
H. Chladil
Affiliation:
Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben, Austria
H. Leitner
Affiliation:
Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben, Austria
H. Clemens
Affiliation:
Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben, Austria
R. Gerling
Affiliation:
Institute for Materials Research, GKSS-Research Centre, D-21502 Geesthacht, Germany
F.-P. Schimansky
Affiliation:
Institute for Materials Research, GKSS-Research Centre, D-21502 Geesthacht, Germany
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Abstract

Massive transformation in high Nb bearing γ-TiAl-based alloys, Ti-45Al-7.5Nb and Ti-46Al-9Nb (at.%), and the thermal stability of the resulting microstructure were investigated. Using a quenching dilatometer, a nearly complete massive transformation in Ti-45Al-7.5Nb was found at about 1050°C after annealing at 1305°C for 10min and subsequent cooling with a rate of 55K/s. Higher starting temperatures and higher cooling rates lead to incomplete massive transformation and small transformed areas situated at the grain-boundary triple points of the parent α-grains are observed. By means of EBSD only in one case the same orientation of the close-packed planes of parent α-grains and of massively transformed γM-areas was observed.

The thermal stability of the microstructure of massively transformed Ti-46Al-9Nb sheet material was tested by annealing samples for 1 hour between 400 and 1200°C. Above 800°C a drop of hardness was measured and X-ray diffraction patterns show an increasing separation of (200)γ and (002)γ reflections as expected from a tetragonal γ-TiAl lattice. After annealing at 1100°C α2-phase segregates at grain boundaries and after 1200°C α2-lamellae appear insides the γM-grains parallel to all four {111}γ-planes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 842: Symposium S – Integrative and Interdisciplinary Aspects of Intermetallics , 2004 , S5.48
Copyright
Copyright © Materials Research Society 2005

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References

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