Martensitic transformation and shape memory effect of Ni49.6Ti45.4Ta5 shape memory alloy

•Ni49.6Ti45.4Ta5 alloy exhibits B2 ↔ B19′ transformation above room temperature.•The Ta-rich (Ta, Ti)2Ni phase is formed in the solution-treated alloy.•The maximum shape memory strain reaches 5.32% after an optimal thermomechanical treatment. NiTiTa shape memory alloys (SMAs) exhibit higher corrosio...

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Bibliographic Details
Published in:Materials letters 2023-04, Vol.337, p.133937, Article 133937
Main Authors: Mei, H., Liu, J.C., Chen, F., Tong, Y.X., Zarinejad, M.
Format: Article
Language:English
Subjects:
Martensite
Microstructure
NiTiTa
Phase transformation
Shape memory
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Summary:•Ni49.6Ti45.4Ta5 alloy exhibits B2 ↔ B19′ transformation above room temperature.•The Ta-rich (Ta, Ti)2Ni phase is formed in the solution-treated alloy.•The maximum shape memory strain reaches 5.32% after an optimal thermomechanical treatment. NiTiTa shape memory alloys (SMAs) exhibit higher corrosion resistance and much better X-ray visibility in comparison with NiTi SMAs. In this work, the martensitic transformation, microstructure, and shape memory effect (SME) of Ni49.6Ti45.4Ta5 SMA are studied. When solution-treated, the alloy undergoes a single-step B2 ↔ B19′ transformation upon cooling and heating, which is gradually shifted to lower temperatures because of thermal cycling. A martensitic microstructure with well-defined twin variants is observed which is beneficial for SME whereas the formation of (Ta, Ti)2Ni phases may deteriorate it. After an optimal thermomechanical treatment, the maximum recovery strain reaches up to 5.32% under a pre-strain of 7%.
ISSN:0167-577X
1873-4979
DOI:10.1016/j.matlet.2023.133937