The microstructure of Ti-Ni-Cu shape memory thin films: a review

Abstract

Ti-Ni-Cu shape memory thin films have attracted more attention as a result of the perfect combination of various advantages such as narrower thermal hysteresis, superior thermal cycling stability, higher strength and long-term functional fatigue. The prominent functional properties were closely related to their specific crystal structure and microstructural features. In the present paper, the microstructure in equiatomic, Ti-rich and (Ni,Cu)-rich shape memory thin films were reviewed. In addition, the corresponding results including martensitic transformation, microstructure and strain recovery characteristics of Ti-Ni-Cu thin films without precipitates and containing different types of precipitates were summarised. Besides, the mechanisms for obtaining the outstanding functional properties are discussed and reviewed, which can offer the theoretical basis to the design of Ti-Ni-Cu shape memory alloy thin film micro actuators with excellent performances.

KEYWORDS:

• Ti-Ni-Cu thin films
• shape memory alloy
• martensite structure
• precipitates

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant Nos. 51801023, 51871080 and 52101231) and the Science Fund of Shandong Laboratory of Advanced Materials and Green Manufacturing (Yantai), AMGM2021F09 as well as the Natural Science Foundation of Shandong Province (No. ZR2021QE044).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 51801023, 51871080, 52101231] and the Science Fund of Shandong Laboratory of Advanced Materials and Green Manufacturing (Yantai), AMGM2021F09 as well as the Natural Science Foundation of Shandong Province [grant number ZR2021QE044].