Magnetic shape memory alloy

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MSM principle: source

Magnetic shape memory alloys (MFGL) (FSMA - ferromagnetic shape memory alloys) are special forms of the shape memory alloys (SMA), which, in addition to the thermal shape memory effect, also cause a significant change in shape due to an external magnetic field exhibit.

introduction

The MFGL are ferromagnetic materials that generate force and movement under moderate magnetic fields. Typically these are mostly single crystal alloys of nickel , manganese and gallium , which are able to generate 6% elongation under external loads of more than 2 N / mm². It can frequencies up to the low kilo hertz range can be achieved. This happens when the material reorientates itself in the ferromagnetic martensitic phase due to the mobility of the twin boundaries in the atomic lattice. Since the martensitic structure is tetragonal, such a microscopic change in orientation also results in a macroscopic change in length of such a sample. This reorientation can take place through external forces (simply pressing on an axis) or due to the anisotropic permeability (direction-dependent magnetic conductivity) through an external magnetic field. This reaction takes place one to two orders of magnitude faster than with thermal shape memory alloys . The most commonly studied alloy is i. A. from about 50% nickel, 25% manganese and 25% gallium (Ni 2 MnGa).

Depending on their structure, commercially available materials can achieve elongations of 6% without external loads at room temperature. While a phase transition between martensite and austenite plays an important role in thermal shape memory alloys (TFGL) , the magnetic shape memory effect occurs exclusively in the martensitic phase. The material has an internal friction that is related to the mobility of the twin boundaries (hence the so-called “twin tension”). This fact enables actuators to be able to hold any position or expansion without external energy supply.

Alloy development

The most studied alloy system are nickel - manganese - gallium - alloys whose intense scientific investigation and commercial usage started in the mid 1990s. In addition, other material systems such as B. iron - palladium Fe-Pd, nickel-iron-gallium Ni-Fe-Ga or from Ni-Mn-Ga derived higher-quality alloys are investigated, which in particular iron, cobalt or copper is added. An important motivation for the development of modified alloys is to find materials with higher phase transition and Curie temperatures, which result in the maximum temperature at which the material can be used. On a modified Ni-Mn-Ga alloy, the magnetic shape memory effect was demonstrated at 80 ° C with a positive working yield.

Magnetic anisotropy

10M structure

In order for the magnetic shape memory effect to occur, the material must have a high direction-dependent (anisotropic) magnetic conductivity ( permeability ). The MFGL have a very large magnetic anisotropy, which influences the force that such an element generates.

structure

The lattice structure is described by a recurring pattern (modulation) in the atomic structure of the unit cell of this alloy. A typical lattice structure of the Ni 2 MnGa alloys has a 10-fold modulated so-called 10M structure, which is also described as (3 ̅ 2) 2. This type of modulation enables a change in length of approx. 6% with MFGL. The 10M structure is often also referred to as the 5M structure, as a periodic structure is achieved when three atomic levels are offset to the right and two to the left, i.e. a total of 5 levels. But the chemical periodicity is only given after 10 levels. In addition, 7M and 14M structures are known which lead to an elongation of more than 10% and so-called non-modulated NM structures with which an elongation of up to 20% is possible.

literature

  1. ↑ Rene Schnetzler: Development of MSM-based dampers and evaluation of market readiness . In: HTWG Konstanz (ed.): Master's thesis . HTWG Konstanz, Konstanz August 2016.
  2. ↑ Hartmut Janocha: Unconventional Actuators: An Introduction . Ed .: Walter de Gruyter. 2nd Edition. Oldenbourg Verlag, 2013, ISBN 978-3-486-71886-7 , p. 324 .
  3. ↑ a b c The MSM NET: The MSM NET. (No longer available online.) June 2015, archived from the original on August 30, 2016 ; accessed on August 30, 2016 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.themsmnet.net
  4. ↑ ETO Group: Magnetoshape Technology. In: ETO. ETO, accessed on August 30, 2016 .
  5. ↑ Magnetic shape memory elements. Goodfellow Cambridge Ltd., accessed September 1, 2016 .
  6. ↑ K. Ullakko: Magnetically controlled shape memory alloys: A new class of actuator materials . In: Journal of Materials Engineering and Performance . tape 5 , no. 3 , ISSN  1059-9495 , p. 405-409 , doi : 10.1007 / BF02649344 ( springer.com [accessed August 30, 2016]).
  7. ↑ Yuanchang Liang, Yuji Sutou, Taishi Wada, Cheng-Chun Lee, M. Taya: Magnetic field-induced reversible actuation using ferromagnetic shape memory alloys . In: Scripta Materialia . tape 48 , no. 10 , May 1, 2003, p. 1415-1419 , doi : 10.1016 / S1359-6462 (03) 00110-6 ( sciencedirect.com [accessed August 30, 2016]).
  8. ^ J. Pons, E. Cesari, C. Seguí, F. Masdeu, R. Santamarta: Ferromagnetic shape memory alloys: Alternatives to Ni – Mn – Ga . In: Materials Science and Engineering: A (=  Proceedings of the 7th European Symposium on Martensitic Transformations, ESOMAT 2006 ). tape 481-482 , May 25, 2008, pp. 57-65 , doi : 10.1016 / j.msea.2007.02.152 ( sciencedirect.com [accessed August 30, 2016]).
  9. ↑ I. Glavatskyy, N. Glavatska, O. Soderberg, S.-P. Hannula, J.-U. Hoffmann: Transformation temperatures and magnetoplasticity of Ni – Mn – Ga alloyed with Si, In, Co or Fe . In: Scripta Materialia . tape 54 , no. 11 , June 1, 2006, p. 1891–1895 , doi : 10.1016 / j.scriptamat.2006.02.010 ( sciencedirect.com [accessed August 30, 2016]).
  10. ↑ Shihai Guo, Yanghuan Zhang, Baiyun Quan, Jianliang Li, Yan Qi: The effect of doped elements on the martensitic transformation in Ni – Mn – Ga magnetic shape memory alloy . In: Smart Materials and Structures . tape 14 , no. 5 , January 1, 2005, ISSN  0964-1726 , p. S236 , doi : 10.1088 / 0964-1726 / 14/5/010 ( iop.org [accessed August 30, 2016]).
  11. ↑ E. Pagounis, A. Laptev, J. Jungwirth, M. Laufenberg, M. Fonin: Magnetomechanical properties of a high-temperature Ni-Mn-Ga magnetic shape memory actuator material . In: Scripta Materialia . tape 88 , October 1, 2014, p. 17-20 , doi : 10.1016 / j.scriptamat.2014.06.013 ( sciencedirect.com [accessed August 30, 2016]).
  12. ↑ a b c Thomas Schiepp: PhD Thesis: A Simulation Method for Design and Development of Magnetic Shape Memory Actuators . Ed .: University of Gloucestershire. Gloucestershire (UK) April 2015, p. 125 ( glos.ac.uk ).
  13. ↑ K. Otsuka, T. Ohba, M. Tokonami, CM Wayman: New description of long period stacking order structures of martensites in β-phase alloys . In: Scripta Metallurgica et Materialia . tape 29 , no. 10 , November 15, 1993, pp. 1359-1364 , doi : 10.1016 / 0956-716X (93) 90139-J ( sciencedirect.com [accessed August 30, 2016]).
  14. ^ SPP 1239. Retrieved August 30, 2016 .
  15. ↑ Chmielus, Markus: Composition, Structure and Magneto-Mechanical Properties of Ni-Mn-Ga Magnetic Shape-Memory Alloys . February 15, 2011.
  16. ↑ A. Sozinov, N. Lanska, A. Soroka, W. Zou: 12% magnetic field-induced strain in Ni-Mn-Ga-based non-modulated martensite . In: Applied Physics Letters . tape 102 , no. 2 , January 14, 2013, ISSN  0003-6951 , p. 021902 , doi : 10.1063 / 1.4775677 ( aip.org [accessed August 30, 2016]).