Superelasticity and shape memory effect under tension and compression in the [001]-oriented crystals of non-equiatomic fenicoalti high entropy alloy

The relationship of annealing and shape memory effect of uniaxially oriented shape memory polyurethane was studied; meanwhile a new method of adjusting shape recovery ratio by annealing was proposed for further consideration. Experiments were designed to compare the influence on length change from annealing and shape memory effect with shape memory polyurethane film at 65°C. We found that for shape memory polyurethane which had residual strain from material processing procedure, annealing and shape memory effect have the same effect on its length change if they are both carried out at the same temperature. It is because annealing and shape memory effect have the same mechanism, which is the change of state from low conformational entropy states to the recovery of a stable high entropy state in the polymer. Moreover, it is proved by experiment that shape recovery ratio of shape memory polyurethane can be adjusted by annealing.

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Microstructure Formation in Cast TiZrHfCoNiCu and CoNiCuAlGaIn High Entropy Shape Memory Alloys: A Comparison

Materials ◽

10.3390/ma12244227 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4227 ◽

Cited By ~ 1

Author(s):

Tetiana A. Kosorukova ◽

Gregory Gerstein ◽

Valerii V. Odnosum ◽

Yuri N. Koval ◽

Hans Jürgen Maier ◽

...

Keyword(s):

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Microstructure Characterization ◽

Microstructure Formation ◽

High Entropy

The present study is dedicated to the microstructure characterization of the as-cast high entropy intermetallics that undergo a martensitic transformation, which is associated with the shape memory effect. It is shown that the TiZrHfCoNiCu system exhibits strong dendritic liquation, which leads to the formation of martensite crystals inside the dendrites. In contrast, in the CoNiCuAlGaIn system the dendritic liquation allows the martensite crystals to form only in interdendritic regions. This phenomenon together with the peculiarities of chemical inhomogeneities formed upon crystallization of this novel multicomponent shape memory alloys systems will be analyzed and discussed.

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Investigation of shape memory effect in Ni-Ti based alloys

Communications in Physics ◽

10.15625/0868-3166/15702 ◽

2021 ◽

Vol 31 (4) ◽

Author(s):

Dan Nguyen Huy ◽

Xuan Hau Kieu ◽

Hai Yen Nguyen ◽

Thi Thanh Pham ◽

Huy Ngoc Nguyen ◽

...

Keyword(s):

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Melt Spinning ◽

High Strength ◽

High Entropy ◽

Practical Applications ◽

Bone Anchors ◽

Research Situation ◽

Initial Results

Shape memory alloys (SMAs) are ones which can return to their original shape under impact of temperature or external magnetic field. The SMAs are capable of many applications in the fields of biomedical, aerospace, microelectronics, automation, for examples, orthodontics, stents, bone anchors, automatic valves, heat sensors, nanotweezers, robots... Recently, researchers have discovered the shape memory effect (SME) on high entropy alloys (HEAs). The combination of superior properties of SMAs and HEAs (high strength, heat resistance, low diffusion coefficient...) would bring useful practical applications in practice. In this paper, we will present an overview of the research situation of SMAs and our initial results obtained on Ni-Ti based alloys of Ni-Ti, Ni-Ti-Zr-Cu-Cr, Ni-Ti-Zr-Cu-Co, Ni-Ti-Zr-Cu-Nb, and Ni-Ti-Zr-Cu-Hf prepared by melt-spinning method.

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A strategy of designing high-entropy alloys with high-temperature shape memory effect

Scientific Reports ◽

10.1038/s41598-019-49529-8 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 7

Author(s):

Je In Lee ◽

Koichi Tsuchiya ◽

Wataru Tasaki ◽

Hyun Seok Oh ◽

Takahiro Sawaguchi ◽

...

Keyword(s):

High Temperature ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Noble Metals ◽

Alloy System ◽

Equilibrium Temperature ◽

High Entropy Alloys ◽

Face Centered Cubic ◽

High Entropy

Abstract Shape memory effect, the ability to recover a pre-deformed shape on heating, results from a reversible martensitic transformation between austenite and martensite phases. Here, we demonstrate a strategy of designing high-entropy alloys (HEAs) with high-temperature shape memory effect in the CrMnFeCoNi alloy system. First, we calculate the difference in Gibbs free energy between face-centered-cubic (FCC) and hexagonal-close-packed (HCP) phases, and find a substantial increase in thermodynamic equilibrium temperature between the FCC and HCP phases through composition tuning, leading to thermally- and stress-induced martensitic transformations. As a consequence, the shape recovery temperature in non-equiatomic CrMnFeCoNi alloys can be increased to 698 K, which is much higher than that of conventional shape memory alloys (SMAs) and comparable to that of B2-based multi-component SMAs containing noble metals (Pd, Pt, etc.) or refractory metals (Zr, Hf, etc.). This result opens a vast field of applications of HEAs as a novel class of cost-effective high-temperature SMAs.

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Tensile Failure of 55-Nitinol Wire

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113858 ◽

1975 ◽

Vol 33 ◽

pp. 46-47

Author(s):

F. I. Grace

Keyword(s):

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Stoichiometric Composition ◽

Tensile Failure ◽

Initial State ◽

Initial Shape ◽

Nitinol Wire ◽

Cscl Type ◽

Shear Transformation

An interest in NiTi alloys with near stoichiometric composition (55 NiTi) has intensified since they were found to exhibit a unique mechanical shape memory effect at the Naval Ordnance Laboratory some twelve years ago (thus refered to as NITINOL alloys). Since then, the microstructural mechanisms associated with the shape memory effect have been investigated and several interesting engineering applications have appeared.The shape memory effect implies that the alloy deformed from an initial shape will spontaneously return to that initial state upon heating. This behavior is reported to be related to a diffusionless shear transformation which takes place between similar but slightly different CsCl type structures.

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