The overarching goal of this research was to generate a menu of shape memory alloys (SMAs) actuator materials capable of meeting the demands of aerospace applications. Material requirements were recognized to meet the demand for high temperature SMAs with actuating temperatures above 85 °C and provide material options capable of performing over 100K actuation cycles. The first study is a preliminary characterization for the down selection of Ni-rich NiTiHf15 compositions chosen for a more in-depth examination of the nano-precipitation and evolution of the H-phase. To make this selection, the effect of Ni content in Ni-rich NiTiHf high temperature shape memory alloys (HTSMAs) on processability, microstructure, and hardness was analyzed for three compositions (Ni50.1TiHf15, Ni50.3TiHf15, Ni50.5TiHf15). Each composition was characterized under three conditions: homogenized, 25%, and 50% thickness reduction through hot-rolling. The second study emphasized the processing and aging response of an industrially produced, hot-extruded Ni50.3Ti29.7Hf20 (at%) HTSMA. The samples were sectioned into two halves with half remaining as-extruded and the other half hot-rolled to a 25% reduction in thickness. A portion of both conditions underwent conventional aging for 3 hours at various temperatures ranging from 450-750 °C, and the other portion was pre-aged for 12 hours at 300 °C followed by conventional aging treatments. After processing, the samples were characterized by differential scanning calorimetry (DSC), Vickers hardness (HV) testing, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron radiation X-ray diffraction (SR-XRD). The relationship between the introduction of texturing, pre-aging, and aging on Ni-rich and high Hf-content compositions was investigated.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc1752389 |
| Date | 12 1900 |
| Creators | Gantz, Faith |
| Contributors | Young, Marcus L, Reidy, Rick, Aouadi, Samir M, Voevodin, Andrey |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | viii, 50 pages, Text |
| Rights | Public, Gantz, Faith, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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