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Structural and Phase Transformations in Thin Film Ti-Aluminides and Ti/Al Multilayers

Published online by Cambridge University Press:  10 February 2011

R. Banerjee ,
S. Swaminathan ,
R. Wheeler  and
H. L. Fraser
R. Banerjee
Affiliation:
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210
S. Swaminathan
Affiliation:
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210
R. Wheeler
Affiliation:
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210
H. L. Fraser
Affiliation:
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210
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Abstract

Multilayered Ti/Al thin films (with nominally equal layer thickness of Ti and Al) have been sputter deposited on oxidized silicon substrates at room temperature. Transmission electron microscopy (TEM) and high resolution electron microscopy have been used to characterize the structure of these multilayers as a function of the layer thickness. Ti changed from an hcp to an fcc and back to an hcp structure on reduction of the layer thickness. Al too changed from an fcc to an hcp structure at a layer thickness of 2.5 nm. The observed structural transitions have been explained on the basis of the Redfield-Zangwill model. Subsequently Ti-aluminide thin films were deposited using a γ-TiAl target. These films were found to be amorphous in the as-deposited condition with crystallites of α-Ti(Al) embedded in the amorphous matrix. On annealing under a protective Ar atmosphere at a temperature of 550 °C, the Ti-aluminide film crystallized into a nanocrystalline two phase microstructure consisting of γ-TiAl and α2-Ti3Al. The crystallization of the aluminide film has been investigated in detail by in-situ annealing experiments on a hot stage in the TEM. The results of this investigation have been discussed in this paper.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 434: Symposium U – Layered Materials for Structural Applications , 1996 , 63
Copyright
Copyright © Materials Research Society 1996

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