Shape memory characteristics of (TiZrHf)50Ni25Co10Cu15 high entropy shape memory alloy

The examination of solid state processes leading to the degradation of the shape memory behaviour is essential with respect to the suitability of shape memory alloys. Besides degradation processes occurring during relatively long periods of time called ageing, bainitic reactions that suddenly degrade the shape memory behaviour were also observed in many Cu-based shape memory alloys. The mechanisms and effects of the bainitic reactions on the shape memory characteristics were investigated in many Cu-based systems, but the kinetic of the reaction was not examined so far. In the present paper, an examination was carried out on a CuAlNiMn and a CuAlNiMnFe shape memory alloy to reveal what kinetic model describes the bainitic reaction occurring and thus completely destroying the shape memory effect during one stage of heating.

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Effect of Solution Treatment on the Shape Memory Functions of (TiZrHf)50Ni25Co10Cu15 High Entropy Shape Memory Alloy

Entropy ◽

10.3390/e21101027 ◽

2019 ◽

Vol 21 (10) ◽

pp. 1027 ◽

Cited By ~ 7

Author(s):

Hao-Chen Lee ◽

Yue-Jin Chen ◽

Chih-Hsuan Chen

Keyword(s):

Martensitic Transformation ◽

Shape Memory Alloy ◽

Shape Memory ◽

Lattice Distortion ◽

Functional Performance ◽

Solution Treatment ◽

Memory Functions ◽

High Entropy ◽

The Matrix ◽

Entropy Effect

This study investigated the effects of solution treatment at 1000 °C on the transformation behaviors, microstructure, and shape memory functions of a novel (TiZrHf)50Ni25Co10Cu15 high entropy shape memory alloy (HESMA). The solution treatment caused partial dissolution of non-oxygen-stabilized Ti2Ni-like phase. This phenomenon resulted in the increment of (Ti, Zr, Hf) content in the matrix and thus increment of the Ms and Af temperatures. At the same time, the solution treatment induced a high entropy effect and thus increased the degree of lattice distortion, which led to increment of the friction force during martensitic transformation, resulting in a broad transformation temperature range. The dissolution of the Ti2Ni-like phase also improved the functional performance of the HESMA by reducing its brittleness and increasing its strength. The experimental results presented in this study demonstrate that solution treatment is an effective and essential way to improve the functional performance of the HESMA.

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Microstructural characterization and shape memory characteristics of the Ni50.3Ti34.7Hf15 shape memory alloy

Acta Materialia ◽

10.1016/j.actamat.2014.09.027 ◽

2015 ◽

Vol 83 ◽

pp. 48-60 ◽

Cited By ~ 69

Author(s):

A. Evirgen ◽

I. Karaman ◽

R. Santamarta ◽

J. Pons ◽

R.D. Noebe

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Microstructural Characterization ◽

Memory Characteristics

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Sputter-Deposited Shape-Memory Alloy Thin Films: Properties and Applications

MRS Bulletin ◽

10.1557/mrs2002.46 ◽

2002 ◽

Vol 27 (2) ◽

pp. 111-114 ◽

Cited By ~ 86

Author(s):

Akira Ishida ◽

Valery Martynov

Keyword(s):

Thin Film ◽

Thin Films ◽

Shape Memory Alloy ◽

Shape Memory ◽

Microelectromechanical Systems ◽

Sputter Deposition ◽

Bulk Materials ◽

Shape Memory Actuators ◽

Sputter Deposited ◽

Memory Characteristics

AbstractShape-memory alloy (SMA) thin films formed by sputter deposition have attracted considerable attention in the last decade. Current intensive research demonstrates that unique fine microstructures are responsible for the superior shape-memory characteristics observed in thin films as compared with bulk materials. Simultaneously, much effort has been undertaken to develop and fabricate micro devices actuated by SMA thin films. This article reviews the research to date on shape-memory behavior and the mechanical properties of SMA thin films in connection with their peculiar microstructures. Promising applications such as microvalves are demonstrated, along with a focused discussion on process-related problems. All of the results indicate that thin-film shape-memory actuators are ready to contribute to the development of microelectromechanical systems.

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