Properties of a Ni19.5Pd30Ti50.5 high-temperature shape memory alloy in tension and compression

Ronald Noebe; Santo Padula II; Glen Bigelow; Orlando Rios; Anita Garg; Brad Lerch

doi:10.1117/12.658023

6 April 2006 Properties of a Ni_19.5Pd₃₀Ti_50.5 high-temperature shape memory alloy in tension and compression

Ronald Noebe, Santo Padula II, Glen Bigelow, Orlando Rios, Anita Garg, Brad Lerch

Proceedings Volume 6170, Smart Structures and Materials 2006: Active Materials: Behavior and Mechanics; 617010 (2006) https://doi.org/10.1117/12.658023
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2006, San Diego, California, United States

Abstract

Potential applications involving high-temperature shape memory alloys have been growing in recent years. Even in those cases where promising new alloys have been identified, the knowledge base for such materials contains gaps crucial to their maturation and implementation in actuator and other applications. We begin to address this issue by characterizing the mechanical behavior of a Ni_19.5Pd₃₀Ti_50.5 high-temperature shape memory alloy in both uniaxial tension and compression at various temperatures. Differences in the isothermal uniaxial deformation behavior were most notable at test temperatures below the martensite finish temperature. The elastic modulus of the material was very dependent on strain level; therefore, dynamic Young's Modulus was determined as a function of temperature by an impulse excitation technique. More importantly, the performance of a thermally activated actuator material is dependent on the work output of the alloy. Consequently, the strain-temperature response of the Ni_19.5Pd₃₀Ti_50.5 alloy under various loads was determined in both tension and compression and the specific work output calculated and compared in both loading conditions. It was found that the transformation strain and thus, the specific work output were similar regardless of the loading condition. Also, in both tension and compression, the strain-temperature loops determined under constant load conditions did not close due to the fact that the transformation strain during cooling was always larger than the transformation strain during heating. This was apparently the result of permanent plastic deformation of the martensite phase with each cycle. Consequently, before this alloy can be used under cyclic actuation conditions, modification of the microstructure or composition would be required to increase the resistance of the alloy to plastic deformation by slip.

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Ronald Noebe, Santo Padula II, Glen Bigelow, Orlando Rios, Anita Garg, and Brad Lerch "Properties of a Ni_19.5Pd₃₀Ti_50.5 high-temperature shape memory alloy in tension and compression", Proc. SPIE 6170, Smart Structures and Materials 2006: Active Materials: Behavior and Mechanics, 617010 (6 April 2006); https://doi.org/10.1117/12.658023

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