Special Issue "Shape Memory Alloys"

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A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 March 2013)

Special Issue Information

Dear Colleagues,

More than half a century has elapsed since research on Au-Cd alloys stimulated a world-wide interest in shape memory and super-elastic behaviour. Both the microscopic and mesoscopic transformation processes, associated with the essential martensitic phase transition have been extensively studied in a wide range of materials. Consequently these materials are finding use as sensors, actuators etc., in fields as diverse as medicine and aviation. Although the phase transition is usually thermally or mechanically driven, more recent research has focused on the ability to do this using magnetic fields in ferromagnetic alloys. However many of the materials studied are brittle which would appear to limit their application. This constraint maybe overcome by incorporating the materials in hybrid composites The possibility of doing this or incorporating shape memory alloys with other smart materials opens up new areas of fundamental and applied research.

Prof. Dr. Kurt R. Ziebeck
Guest Editor

Submission

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Keywords

  • shape memory
  • phase transitions
  • magnetism
  • transport properties
  • neutron
  • xray and electron scattering
  • smart materials

Published Papers (7 papers)

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Research

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Open AccessArticle The Thermal Transformation Arrest Phenomenon in NiCoMnAl Heusler Alloys
Metals 2013, 3(3), 298-311; doi:10.3390/met3030298
Received: 20 May 2013 / Revised: 26 June 2013 / Accepted: 14 August 2013 / Published: 22 August 2013
Cited by 14 | PDF Full-text (3007 KB) | HTML Full-text | XML Full-text
Abstract
In this report, we present findings of systematic research on NiCoMnAl alloys, with the purpose of acquiring a higher thermal transformation arrest temperature (TA). By systematic research, TA in the NiCoMnAl alloy systems was raised up to 190 K, compared to the highest
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In this report, we present findings of systematic research on NiCoMnAl alloys, with the purpose of acquiring a higher thermal transformation arrest temperature (TA). By systematic research, TA in the NiCoMnAl alloy systems was raised up to 190 K, compared to the highest TA of 130 K in NiCoMnIn. For a selected alloy of Ni40Co10Mn33Al17, magnetization measurements were performed under a pulsed high magnetic field, and the critical magnetic field-temperature phase diagram was determined. The magnetic phase diagram for Ni50-xCoxMn50-yAly was also established. Moreover, from the discussion that the formerly called “kinetic arrest phenomenon” has both thermodynamic and kinetic factors, we suggest a terminology change to the “thermal transformation arrest phenomenon”. Full article
(This article belongs to the Special Issue Shape Memory Alloys)
Open AccessArticle Mössbauer Spectroscopy Studies on Magnetic Properties for 57Fe-substituted Ni-Mn-Sn Metamagnetic Shape Memory Alloys
Metals 2013, 3(2), 225-236; doi:10.3390/met3020225
Received: 10 April 2013 / Revised: 20 May 2013 / Accepted: 23 May 2013 / Published: 3 June 2013
Cited by 1 | PDF Full-text (899 KB) | HTML Full-text | XML Full-text
Abstract
In order to investigate the Fe substituted effects on the magnetic properties of the Ni-Mn-Sn metamagnetic shape memory alloys, magnetization and the Mössbauer spectroscopy measurements were carried out with using 57Fe-doped specimens of Ni2Mn1.48−x57FexSn
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In order to investigate the Fe substituted effects on the magnetic properties of the Ni-Mn-Sn metamagnetic shape memory alloys, magnetization and the Mössbauer spectroscopy measurements were carried out with using 57Fe-doped specimens of Ni2Mn1.48−x57FexSn0.52 (x = 0.02, 0.04 and 0.08). Singlet-type Mössbauer spectra were clearly observed for x = 0.02 and 0.04 just below the martensitic transformation temperature, TM, and above the Curie temperature, TC, in the austenite phase. It was clear that the magnetic state in the martensite phase just below TM was paramagnetic for x = 0.02 and 0.04. In further doped 57Fe to Ni2Mn1.48Sn0.52, TC in the austenite phase slightly increased. However, the value of TM significantly decreased. As a result, martensite phase with small spontaneous magnetization directly transformed to the ferromagnetic austenite phase during heating for x = 0.08. These results obtained from the Mössbauer spectra were consistent with the results of the magnetic measurements in this study and the phase diagram reported by Fukushima et al. for normal Fe-doped Ni2Mn1.48−xFexSn0.52 alloys. The breakdown of the general rule, in which the ferromagnetic shape memory alloys with larger value of the valence electrons per atom, e/a, showed higher TM, was also appeared in Ni2Mn1.48−xFexSn0.52 alloys, being similar to Ni2Mn1−xFexGa alloys. Full article
(This article belongs to the Special Issue Shape Memory Alloys)
Open AccessArticle Experimental Study of Helical Shape Memory Alloy Actuators: Effects of Design and Operating Parameters on Thermal Transients and Stroke
Metals 2013, 3(1), 123-149; doi:10.3390/met3010123
Received: 22 December 2012 / Revised: 3 February 2013 / Accepted: 5 February 2013 / Published: 18 February 2013
Cited by 6 | PDF Full-text (431 KB) | HTML Full-text | XML Full-text
Abstract
Shape memory alloy actuators’ strokes can be increased at the expense of recovery force via heat treatment to form compressed springs in their heat-activated, austenitic state. Although there are models to explain their behaviour, few investigations present experimental results for support or validation.
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Shape memory alloy actuators’ strokes can be increased at the expense of recovery force via heat treatment to form compressed springs in their heat-activated, austenitic state. Although there are models to explain their behaviour, few investigations present experimental results for support or validation. The aim of the present paper is to determine via experimentation how certain parameters affect a helical shape memory alloy actuator’s outputs: its transformation times and stroke. These parameters include wire diameter, spring diameter, transition temperature, number of active turns, bias force and direct current magnitude. Six investigations were performed: one for each parameter manipulation. For repeatability and to observe thermo-mechanical training effects, the springs were cyclically activated. The resultant patterns were compared with results predicted from one-dimensional models to elucidate the findings. Generally, it was observed that the transformation times and strokes converged at changing stress levels; the convergence is likely the peak where the summation of elastic stroke and transformation stroke has reached its maximum. During cyclic loading, the actuators’ strokes decreased to a converged value, particularly at larger internal stresses; training should therefore be performed prior to the actuator’s implementation for continual use applications. Full article
(This article belongs to the Special Issue Shape Memory Alloys)
Open AccessArticle Magnetic Moment of Cu-Modified Ni2MnGa Magnetic Shape Memory Alloys
Metals 2013, 3(1), 114-122; doi:10.3390/met3010114
Received: 4 January 2013 / Revised: 24 January 2013 / Accepted: 25 January 2013 / Published: 4 February 2013
Cited by 4 | PDF Full-text (192 KB) | HTML Full-text | XML Full-text
Abstract
The magnetization measurements at 5 K were carried out for Ni2Mn1xCuxGa (0 ≤ x ≤ 0.40) and Ni2MnGa1yCuy(0 ≤ y ≤ 0.25) alloys. All of the magnetization
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The magnetization measurements at 5 K were carried out for Ni2Mn1 xCuxGa (0 ≤ x ≤ 0.40) and Ni2MnGa1 yCuy (0 ≤ y ≤ 0.25) alloys. All of the magnetization curves are characteristic of ferromagnetism or ferrimagnetism. By using Arrott plot analysis the spontaneous magnetization of all samples was determined from the magnetization curves. The magnetic moment per formula unit, μs, at 5 K was estimated from the spontaneous magnetization. For Ni2Mn1 xCuxGa (0 ≤ x ≤ 0.40) alloys μs at 5 K decreases linearly with increasing x. On the other hand, the μs at 5 K for Ni2MnGa1 yCuy (0 ≤ y ≤ 0.25) alloys decreases more steeply with increasing x compared to the μs for Ni2Mn1 xCuxGa (0 ≤ x ≤ 0.40) alloys. On the basis of the experimental results, the site-occupation configurations of Ni2Mn1 xCuxGa (0 ≤ x ≤ 0.40) and Ni2MnGa1 yCuy (0 ≤ y ≤ 0.25) alloys are proposed. Full article
(This article belongs to the Special Issue Shape Memory Alloys)
Open AccessArticle Exchange Bias and Inverse Magnetocaloric Effect in Co and Mn Co-Doped Ni2MnGa Shape Memory Alloy
Metals 2013, 3(1), 69-76; doi:10.3390/met3010069
Received: 13 December 2012 / Revised: 8 January 2013 / Accepted: 17 January 2013 / Published: 25 January 2013
Cited by 4 | PDF Full-text (323 KB) | HTML Full-text | XML Full-text
Abstract
Exchange bias effect observed in the Ni1.68Co0.32Mn1.20Ga0.80 alloy confirms the coexistence of antiferromagnetic and ferromagnetic phases in the martensite phase. A large inverse magnetocaloric effect has been observed within the martensitic transformation temperature range, which is
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Exchange bias effect observed in the Ni1.68Co0.32Mn1.20Ga0.80 alloy confirms the coexistence of antiferromagnetic and ferromagnetic phases in the martensite phase. A large inverse magnetocaloric effect has been observed within the martensitic transformation temperature range, which is originated from modified magnetic order through magnetic-field-induced phase transformation from partially antiferromagnetic martensite to ferromagnetic austenite. The magnetic entropy change is 16.2 J kg−1 K−1 at 232 K under ΔH = 60 kOe, with the net refrigerant capacity of 68 J kg−1. These properties indicate Co and Mn co-doped Ni2MnGa alloy is a multifunctional material potentially suitable for magnetic refrigeration and spintronics applications. Full article
(This article belongs to the Special Issue Shape Memory Alloys)

Review

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Open AccessReview Transformation Volume Effects on Shape Memory Alloys
Metals 2013, 3(3), 237-282; doi:10.3390/met3030237
Received: 1 April 2013 / Revised: 12 June 2013 / Accepted: 13 June 2013 / Published: 2 July 2013
Cited by 13 | PDF Full-text (1013 KB) | HTML Full-text | XML Full-text
Abstract
It is generally accepted that the martensitic transformations (MTs) in the shape memory alloys (SMAs) are mainly characterized by the shear deformation of the crystal lattice that arises in the course of MT, while a comparatively small volume change during MT is considered
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It is generally accepted that the martensitic transformations (MTs) in the shape memory alloys (SMAs) are mainly characterized by the shear deformation of the crystal lattice that arises in the course of MT, while a comparatively small volume change during MT is considered as the secondary effect, which can be disregarded when the basic characteristics of MTs and functional properties of SMAs are analyzed. This point of view is a subject to change nowadays due to the new experimental and theoretical findings. The present article elucidates (i) the newly observed physical phenomena in different SMAs in their relation to the volume effect of MT; (ii) the theoretical analysis of the aforementioned volume-related phenomena. Full article
(This article belongs to the Special Issue Shape Memory Alloys)
Open AccessReview Magneto-Structural Properties of Ni2MnGa Ferromagnetic Shape Memory Alloy in Magnetic Fields
Metals 2013, 3(2), 202-224; doi:10.3390/met3020202
Received: 8 March 2013 / Revised: 24 April 2013 / Accepted: 10 May 2013 / Published: 23 May 2013
Cited by 5 | PDF Full-text (707 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this review was to investigate the correlation between magnetism and crystallographic structures as it relates to the martensite transformation of Ni2MnGa type alloys, which undergo martensite transformation below the Curie temperature. In particular, this paper focused on the
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The purpose of this review was to investigate the correlation between magnetism and crystallographic structures as it relates to the martensite transformation of Ni2MnGa type alloys, which undergo martensite transformation below the Curie temperature. In particular, this paper focused on the physical properties in magnetic fields. Recent researches show that the martensite starting temperature (martensite transformation temperature) TM and the martensite to austenite transformation temperature (reverse martensite temperature) TR of Fe, Cu, or Co-doped Ni–Mn–Ga ferromagnetic shape memory alloys increase when compared to Ni2MnGa. These alloys show large field dependence of the martensite transformation temperature. The field dependence of the martensite transformation temperature, dTM/dB, is −4.2 K/T in Ni41Co9Mn32Ga18. The results of linear thermal strain and magnetization indicate that a magneto-structural transition occurred at TM and magnetic field influences the magnetism and also the crystal structures. Magnetocrystalline anisotropy was also determined and compared with other components of Ni2MnGa type shape memory alloys. In the last section, magnetic field-induced strain and magnetostriction was determined with some novel alloys. Full article
(This article belongs to the Special Issue Shape Memory Alloys)

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