Magnetic-field-induced strains in polycrystalline Ni-Mn-Ga at room temperature

Ullakko, K.; Ezer, Y.; Sozinov, A.; Kimmel, G.; Yakovenko, P.; Lindroos, V.K.

doi:10.1016/s1359-6462(00)00610-2

Cited by 108 publications

(58 citation statements)

References 13 publications

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“…1). Among ferromagnetic shape memory alloys, the largest magneticfield-induced strains arising from conversion of martensitic variants under action of a magnetic field 2,3) or caused by the shift of the martensitic transition temperature 4,5) have been observed in the most intensively studied Ni 2 MnGa alloy system. Ni 2 MnGa is a representative of Mn-containing Heusler alloys.…”

Section: Introductionmentioning

confidence: 99%

Influence of Fe and Co on Phase Transitions in Ni-Mn-Ga Alloys

et al. 2003

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Differential scanning calorimetry (DSC) and magnetic measurements were performed to study the influence of ferromagnetic 3-d transition elements Fe and Co on structural and magnetic properties of ferromagnetic shape memory alloys Ni 2 MnGa. Addition of Fe or Co on the Ni sites decreases the temperature of martensitic phase transition T m , whereas addition of Co on the Mn sites results in a considerable increase of T m . Magnetic measurement revealed that Curie temperature T C increases upon substitution of Fe or Co for Ni. This observation is of importance for design of high temperature ferromagnetic shape memory alloys.

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Section: Introductionmentioning

confidence: 99%

Influence of Fe and Co on Phase Transitions in Ni-Mn-Ga Alloys

et al. 2003

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“…The back-reflection Laue diffraction patterns have been obtain from the same place of plane perpendicular to the C-direction. The lattice parameters, a = 0.5944 and c = 0.5617 nm (in cubic coordinates) [11], were used for indexing of the Laue diffraction patterns and for the angle calculations. In the Fig.…”

Section: Resultsmentioning

confidence: 99%

Large magnetic-field-induced strains in Ni-Mn-Ga alloys in rotating magnetic field

Sozinov¹,

Ezer²,

Kimmel

et al. 2001

J. Phys. IV France

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Abstract:A single-crystal samples of near-stoichiometric Ni 2 MnGa alloys with large magnetic field induced strain (MSM effect) at room temperature have been investigated. It was found that there is a reversible reorientation of easy magnetization direction and magnetic domain structure under applied magnetic field. By means of x-ray Laue diffraction method and difractometric analysis it was ascertained that these phenomena are connected with the growth of martensitic twin variant with the short crystallographic axis (c-axis) directed along the applied magnetic field. Furthermore, by means magneto-optical investigations we have found the correlation between martensitic microstructure and magnetic domain structure. The field-induced reorientation of martensite was able to change the dimensional lengths of the samples more than 4.5 %. 1.IntroductionMagnetic field control of the shape of ferromagnetic alloys with martensitic structure was suggested recently [1,2]. Such materials are highly beneficial for actuators [3,4]. Field-induced strains, larger than 4 %, have been observed in the single-crystal Ni2MnGa alloys [5,6]. There are no detailed studies concerning the martensitic microstructure changes connected with MSM (magnetic shape memory) effect. The aim of this work was to fill up this gap. 2.Experimental proceduresThe alloy Ni4g.7Mn3o.iGa2i.3 was melted in an induction furnace in argon atmosphere. The composition of the alloy was measured by wave-length dispersive spectroscopy (WDS). After homogenization at 1000 C during 3 days and aging at 800 C 1 day the alloy was air cooled to room temperature. X-ray diffraction measurements revealed the Heusler type ordered structure (L2y) for the alloy in austenitic state. Martensitic transformation points M s , Mf, A s , A/, and Curie point T c were measured using low field ac magnetic susceptibility technique (M,=29° C, M f = 26° C, A s = 32° C, A f = 35° C, T c = 99° C). Samples for magnetic investigation with dimensions of 4x4x4 mm were cut using spark cutting machine and one single Ni4s.7Mn30.1Ga21.3 grain.All the M-H curves were obtained by using a vibrating sample magnetometer (VSM). The specimen stage was mounted between the pole pieces of a 1 T electromagnet and could be rotated for different field orientations. In all measurements the rotation of the samples was carried out at zero magnetic field. Strains induced by magnetic field were measured by strain gauges. The rather large changes in the sample shape and size gave us the possibility to confirm the strain gauge data by micrometric measurements. Temperatures were carefully controlled with a temperature control unit, i.e. a large volume alcohol circulator.Back-reflection Laue technique was used to determine the change in an orientation of crystals. X-ray tube with W-anode was used. A low voltage level V = 12 kV (/ = 30 mA) was applied in order to avoid the characteristic line effect and to decrease the fluorescent radiation from sample. The distance between the film Article published online by EDP Sciences a...

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“…In comparison to our work, the following are examples of other work on polycrystalline NiMnGa samples. Ullakko et al (Ref 8,9) reported on MFIS in polycrystals and by thermo-mechanical treatment. But there is no information about the change in microstructure, the data are similar to the single crystal.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Variant Orientation Before and After Compression in Polycrystalline Ni50Mn29Ga21 MSMA

Hürrich

Wendrock

Pötschke

et al. 2009

J. of Materi Eng and Perform

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This paper deals with the microstructure and plastic deformation of Ni 50 Mn 29 Ga 21 ferromagnetic shape memory alloys. In contrast to conventional shape memory alloys, plastic deformation in the martensitic phase, which is due to twin boundary motion, may be caused not only by mechanical stress but also by an external magnetic field. The polycrystalline sample was prepared by directional solidification with a texture parallel to the heat flow. Afterwards, a heat treatment follows for chemical homogenization and stress relaxation in the austenitic state. The configuration of the twin boundaries was analyzed before and after compressing the samples. The microstructure after compression was related to the magnetic properties.

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Magnetic-field-induced strains in polycrystalline Ni-Mn-Ga at room temperature

Cited by 108 publications

References 13 publications

Influence of Fe and Co on Phase Transitions in Ni-Mn-Ga Alloys

Influence of Fe and Co on Phase Transitions in Ni-Mn-Ga Alloys

Large magnetic-field-induced strains in Ni-Mn-Ga alloys in rotating magnetic field

Analysis of Variant Orientation Before and After Compression in Polycrystalline Ni50Mn29Ga21 MSMA

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