Constant-Strain Thermal Cycling of a Ni50.3Ti29.7Hf20 High-Temperature Shape Memory Alloy

• Published in: Shape memory and superelasticity : advances in science and technology Vol. 2; no. 2; pp. 218 - 227
• Main Authors: Benafan, O., Noebe, R. D., Halsmer, T. J., Padula, S. A., Bigelow, G. S., Gaydosh, D. J., Garg, A.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2016; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Materials Science; Thermal stress; Training; Recovery stress; High-temperature shape memory alloy; Constant-strain; NiTiHf
• ISSN: 2199-384X; 2199-3858
• DOI: 10.1007/s40830-016-0068-x

The effect of various pre-straining routines on the recovery stresses of a Ni-rich Ni 50.3 Ti 29.7 Hf 20 high-temperature shape memory alloy was investigated in tension and compression. The recovery stresses, obtained by means of constant-strain thermal cycling, were evaluated after isothermal (up to ±2 % applied strain at room temperature) or after isobaric thermal cycling at stress levels between ±100 and 400 MPa. The material exhibited high force generation capability with recovery stresses of nearly 1.5 GPa on the first cycle under particular pre-strain conditions. The recovery stresses are shown to decay during subsequent cycles using an upper cycle temperature of 300 °C with a saturated stress level nearing 1.1 GPa in compression.