THE USE OF SHAPE-MEMORY ALLOYS FOR MECHANICAL REFRIGERATION

2009 ◽  
Vol 02 (02) ◽  
pp. 73-78 ◽  
Author(s):  
LLUÍS MAÑOSA ◽  
ANTONI PLANES ◽  
EDUARD VIVES ◽  
ERELL BONNOT ◽  
RICARDO ROMERO
Keyword(s):  
Shape Memory Alloys ◽  
Single Crystal ◽  
Shape Memory ◽  
Large Temperature ◽  
Martensitic Transition ◽  
Stress Strain ◽  
Temperature Changes ◽  
Entropy Changes ◽  
Elastocaloric Effect ◽  
Different Temperatures

This letter reports on stress–strain experiments on a Cu – Zn – Al single crystal performed using a purpose-built tensile device which enables the load applied to the specimen to be controlled while elongation is continuously monitored. From the measured isothermal tensile curves, the stress-induced entropy changes are obtained at different temperatures. These data quantify the elastocaloric effect associated with the martensitic transition in shape-memory alloys. The large temperature changes estimated for this effect, suggest the possibility of using shape-memory alloys as mechanical refrigerators.

Large and reversible elastocaloric effect near room temperature in a Ga-doped Ni–Mn–In metamagnetic shape-memory alloy

2017 ◽  
Vol 10 (01) ◽  
pp. 1740007 ◽  
Author(s):  
Juan-Pablo Camarillo ◽  
Christian-Omar Aguilar-Ortiz ◽  
Horacio Flores-Zúñiga ◽  
David Ríos-Jara ◽  
Daniel-Enrique Soto-Parra ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Room Temperature ◽  
Entropy Change ◽  
Martensitic Transition ◽  
Ferromagnetic Shape Memory Alloy ◽  
Temperature Changes ◽  
Elastocaloric Effect ◽  
Magnetocaloric Materials ◽  
Ferromagnetic Shape Memory

We report a giant elastocaloric effect near room temperature in a polycrystalline Ga-doped Ni–Mn–In ferromagnetic shape-memory alloy. The elastocaloric effect has been quantified by measuring both isothermal stress-induced entropy changes and adiabatic stress-induced temperature changes. A reproducible maximum entropy change, [Formula: see text] 25 [Formula: see text][Formula: see text][Formula: see text], upon cycling across the martensitic transition was obtained by application of a compressive stress of 100[Formula: see text]MPa. The corresponding maximum amount of cooling, [Formula: see text][Formula: see text]K, was measured when this stress was rapidly removed. These values are comparable with those reported for giant magnetocaloric materials, which are induced by application and release of a high magnetic field. Therefore, the studied material is a good candidate to be used in solid-state refrigeration devices based on the elastocaloric effect.

scholarly journals Elastocaloric Effect Associated with the Martensitic Transition in Shape-Memory Alloys

2008 ◽  
Vol 100 (12) ◽  
Author(s):  
Erell Bonnot ◽  
Ricardo Romero ◽  
Lluís Mañosa ◽  
Eduard Vives ◽  
Antoni Planes
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensitic Transition ◽  
Elastocaloric Effect

scholarly journals Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression

2016 ◽  
Vol 374 (2074) ◽  
pp. 20150309 ◽  
Author(s):  
Suxin Qian ◽  
Yunlong Geng ◽  
Yi Wang ◽  
Thomas E. Pillsbury ◽  
Yoshiharu Hada ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Latent Heat ◽  
Maximum Stress ◽  
Compression Tests ◽  
Adiabatic Condition ◽  
Scanning Calorimetry ◽  
Recoverable Strain ◽  
Temperature Changes ◽  
Elastocaloric Effect

This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu 68 Al 16 Zn 16 (CuAlZn) and Cu 73 Al 15 Mn 12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s −1 (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (Δ T ad ) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g −1 for the CuAlZn alloy and 5.0 J g −1 for the CuAlMn alloy. Potential coefficients of performance (COP mat ) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COP mat of approximately 13.3 for CuAlMn was obtained. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

Multivariant Formulation of the Thermomechanically Coupled Mu¨ller-Achenbach-Seelecke-Model for Shape Memory Alloys

2009 ◽  
Author(s):  
Oliver Kastner ◽  
Frank Richter ◽  
Gunther Eggeler
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Axial Loading ◽  
Rate Equations ◽  
Variable Load ◽  
Free Energy Function ◽  
Stress Strain ◽  
Temperature Changes ◽  
Stress States ◽  
Shrink Fit

Temperature changes caused by latent transformation heats are an integral part of the behavior of shape memory alloys and inevitably couple the thermal and the mechanical fields. This general behavior is covered by the Mu¨ller-Achenbach-Seelecke (MAS) model. Its versatility has been documented extensively in the literature. In the original formulation the MAS model is restricted to uniaxial states of stress in a SMA, which limits its application to cases where such stress states prevail, such as axial loading in wires and trusses, as well as pure beam bending, pure torsion and shrink-fit problems. Unreliable results, however are expected under arbitrary multiaxial loading conditions. To overcome this limitation we present an extension of the model capable of arbitrary stress/strain/temperature states in 3D. Our model adopts ideas presented by Xie but employs a different non-convex free energy function. Rate equations are employed to model temperature or stress/strain induced transformations between austenite and eight variants of martensite present in the model. As the MAS model, the multi-variant model is capable of fully-coupled thermo-mechanical processes which is shown by simulations of temperature-induced processes, quasiplasticity and pseudoelasticity under variable load directions. At the present level of sophistication, the model is restricted to single crystalline SMA. All examples are explained by the use of a standalone model implementation. The model is intended for future implementation into the finite-element-method environment ABAQUS™ to provide a powerful tool useful in the framework of engineering design studies, especially in situations which require non-isothermal conditions and phase transitions.

Effects of Annealing on Microstructure and Martensitic Transition of Ni-Mn-Co-In Ferromagnetic Shape Memory Alloys

2011 ◽  
Vol 674 ◽  
pp. 171-175
Author(s):  
Katarzyna Bałdys ◽  
Grzegorz Dercz ◽  
Łukasz Madej
Keyword(s):  
Electron Microscopy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Smart Materials ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Ferromagnetic Shape Memory Alloys ◽  
Initial State ◽  
X Ray ◽  
Ferromagnetic Shape Memory

The ferromagnetic shape memory alloys (FSMA) are relatively the brand new smart materials group. The most interesting issue connected with FSMA is magnetic shape memory, which gives a possibility to achieve relatively high strain (over 8%) caused by magnetic field. In this paper the effect of annealing on the microstructure and martensitic transition on Ni-Mn-Co-In ferromagnetic shape memory alloy has been studied. The alloy was prepared by melting of 99,98% pure Ni, 99,98% pure Mn, 99,98% pure Co, 99,99% pure In. The chemical composition, its homogeneity and the alloy microstructure were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The phase composition was also studied by X-ray analysis. The transformation course and characteristic temperatures were determined by the use of differential scanning calorimetry (DSC) and magnetic balance techniques. The results show that Tc of the annealed sample was found to decrease with increasing the annealing temperature. The Ms and Af increases with increasing annealing temperatures and showed best results in 1173K. The studied alloy exhibits a martensitic transformation from a L21 austenite to a martensite phase with a 7-layer (14M) and 5-layer (10M) modulated structure. The lattice constants of the L21 (a0) structure determined by TEM and X-ray analysis in this alloy were a0=0,4866. The TEM observation exhibit that the studied alloy in initial state has bigger accumulations of 10M and 14M structures as opposed from the annealed state.

A phenomenological model for thermally-induced hysteresis in polycrystalline shape memory alloys with internal loops

2021 ◽  
pp. 1045389X2110482
Author(s):  
Yuxiang Han ◽  
Haoyuan Du ◽  
Linxiang Wang ◽  
Roderick Melnik
Keyword(s):  
Shape Memory Alloys ◽  
Single Crystal ◽  
Shape Memory ◽  
Phenomenological Model ◽  
Landau Theory ◽  
Thermally Induced ◽  
First Order ◽  
Proposed Model ◽  
Crystal Model ◽  
Hysteretic Response

In the current study, a 1-D phenomenological model is constructed to capture the temperature-induced hysteretic response in polycrystalline shape memory alloys (SMAs). The martensitic and austenitic transformations are regarded as the first-order transitions. A differential single-crystal model is formulated on the basis of Landau theory. It is assumed that the transformation temperatures follow the normal distribution among the grains due to the anisotropic stress field developed in the material. The polycrystalline hysteretic response is expressed as the integration of single-crystal responses. Besides, the prediction strategy for incomplete transitions is presented, and the first-order reversal curves are obtained via density reassignment. The proposed model is numerically implemented for validation. Comparisons between the modeling results and the experimental ones demonstrate the capability of the proposed model in addressing the hysteresis in thermally-induced phase transformations.

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