PSI - Issue 69

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ScienceDirect

Procedia Structural Integrity 69 (2025) 26–34

13th European Symposium on Martensitic Transformation 2024 (ESOMAT 2024) Development of Ni 3 Ta-based High Temperature Shape Memory Alloys Alberto Coda*, Jannis Nicolas Lemke, Carlo Alberto Biffi, Jacopo Fiocchi, Ausonio Tuissi CNR-ICMATE, National Research Council of Italy – Institute of Condensed Matter Chemistry and Technologies for Energy, Via Previati 1E, Lecco, 23900, Italy. Abstract The development of shape memory alloys operating at temperatures above 373K is a research topic relevant for designing new actuators/sensors able to exploit exhaustive gases and, in general, to increase the working temperature range of the conventional NiTi alloys. The Ni 3 Ta binary system can be considered a promising intermetallic compound because it offers transformation temperatures above 200°C and appears stable under thermal cycling. Like several HTSMAs, this alloy suffers from a poor plastic deformation workability, caused by its coarse microstructure and intrinsic brittleness. In this work, an alloying approach was evaluated with the goal of refining the microstructure without altering the transformation temperatures. Therefore, the alloy chemistry of Ni 3 Ta was modified by the addition of Cu or Co. Furthermore, the effect of heat treatments to tailor the microstructure was explored. The transformation temperatures of samples were characterized by Differential Scanning Calorimetry, the microstructure by Scanning Electron Microscopy and X-Ray Diffraction, and the mechanical properties by microhardness testing. It was observed that Co does not significantly affect the transformation temperatures, while the addition Cu decreases themslightly. Heat treatments were used to affect hardness and transformation temperatures; however, the alloy functional properties proved to be rather stable. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Guest Editors

Keywords: HT SMAs, martensitic transformation, mechanical response.

* Corresponding author. Tel.: E-mail address:: albertocoda@cnr.it

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Guest Editors 10.1016/j.prostr.2025.07.004