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Proceedings Paper

Characterization of ternary NiTiPt high-temperature shape memory alloys
Author(s): Orlando Rios; Ronald Noebe; Tiffany Biles; Anita Garg; Anna Palczer; Daniel Scheiman; Hans Jürgen Seifert; Michael Kaufman
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Paper Abstract

Pt additions substituted for Ni in NiTi alloys are known to increase the transformation temperature of the alloy but only at fairly high Pt levels. However, until now only ternary compositions with a very specific stoichiometry, Ni50-xPtxTi50, have been investigated and then only to very limited extent. In order to learn more about this potential high-temperature shape memory alloy system, a series of over twenty alloys along and on either side of a line of constant stoichiometry between NiTi and TiPt were arc melted, homogenized, and characterized in terms of their microstructure, transformation temperatures, and hardness. The resulting microstructures were examined by scanning electron microscopy and the phase compositions quantified by energy dispersive spectroscopy. "Stoichiometric" compositions along a line of constant stoichiometry between NiTi to TiPt were essentially single phase but any deviations from a stoichiometry of (Ni,Pt)50Ti50 resulted in the presence of at least two different intermetallic phases, depending on the overall composition of the alloy. Essentially all alloys, whether single or two-phase, still under went a martensitic transformation. It was found that the transformation temperatures were depressed with initial Pt additions but at levels greater than 10 at.% the transformation temperature increased linearly with Pt content. Also, the transformation temperatures were relatively insensitive to alloy stoichiometry within the range of alloys examined. Finally, the dependence of hardness on Pt content for a series of Ni50-xPtxTi50 alloys showed solution softening at low Pt levels, while hardening was observed in ternary alloys containing more than about 10 at.% Pt. On either side of these "stoichiometric" compositions, hardness was also found to increase significantly.

Paper Details

Date Published: 16 May 2005
PDF: 12 pages
Proc. SPIE 5761, Smart Structures and Materials 2005: Active Materials: Behavior and Mechanics, (16 May 2005); doi: 10.1117/12.599608
Show Author Affiliations
Orlando Rios, Univ. of Florida (United States)
Ronald Noebe, NASA Glenn Research Ctr. (United States)
Tiffany Biles, NASA Glenn Research Ctr. (United States)
Anita Garg, NASA Glenn Research Ctr. (United States)
Anna Palczer, NASA Glenn Research Ctr. (United States)
Daniel Scheiman, NASA Glenn Research Ctr. (United States)
Hans Jürgen Seifert, Univ. of Florida (United States)
Michael Kaufman, Univ. of North Texas (United States)

Published in SPIE Proceedings Vol. 5761:
Smart Structures and Materials 2005: Active Materials: Behavior and Mechanics
William D. Armstrong, Editor(s)

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