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Development and Characterization of Improved NiTiPd High-Temperature Shape-Memory Alloys by Solid-Solution Strengthening and Thermomechanical ProcessingThe need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently motivating research in high-temperature shape-memory alloys (HTSMA) with transformation temperatures greater than 100 C. One of the basic high-temperature alloys investigated to fill this need is Ni(19.5)Ti(50.5)Pd30. Initial testing has indicated that this alloy, while having acceptable work characteristics, suffers from significant permanent deformation (or ratcheting) during thermal cycling under load. In an effort to overcome this deficiency, various solid-solution alloying and thermomechanical processing schemes were investigated. Solid-solution strengthening was achieved by substituting 5at% gold or platinum for palladium in Ni(19.5)Ti(50.5)Pd30, the so-called baseline alloy, to strengthen the martensite and austenite phases against slip processes and improve thermomechanical behavior. Tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared. The relative difference in yield strength between the martensite and austenite phases and the dimensional stability of the alloy were improved by the quaternary additions, while work output was only minimally impacted. The three alloys were also thermomechanically processed by cycling repeatedly through the transformation range under a constant stress. This so-called training process dramatically improved the dimensional stability in these samples and also recovered the slight decrease in work output caused by quaternary alloying. An added benefit of the solid-solution strengthening was maintenance of enhanced dimensional stability of the trained material to higher temperatures compared to the baseline alloy, providing a greater measure of over-temperature capability.
Document ID
20110001637
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Bigelow, Glen (NASA Glenn Research Center Cleveland, OH, United States)
Noebe, Ronald (NASA Glenn Research Center Cleveland, OH, United States)
Padula, Santo, II (NASA Glenn Research Center Cleveland, OH, United States)
Garg, Anita (NASA Glenn Research Center Cleveland, OH, United States)
Olson, David (Colorado School of Mines Golden, CO, United States)
Date Acquired
August 25, 2013
Publication Date
January 1, 2006
Subject Category
Metals And Metallic Materials
Report/Patent Number
ASM Paper 12689
E-15739
Meeting Information
Meeting: International Conference on Shape Memory and Superelastic Technologies
Location: Pacific Grove, CA
Country: United States
Start Date: May 7, 2006
End Date: May 11, 2006
Funding Number(s)
PROJECT: Proj. IRD04-40/49
WBS: WBS 953033.01.03.17
Distribution Limits
Public
Copyright
Public Use Permitted.

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