Evolution of local strain bands of different orientation in single crystalline Ni–Mn–Ga foils under tension

Pinneker, Viktor; R.Yin,; Eberl, C.; Sozinov, A.; Ezer, Y.; Kohl, Manfred

doi:10.1016/j.jallcom.2012.03.004

Cited by 15 publications

(4 citation statements)

References 15 publications

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“…The smaller magnetostrain observed here is due to inactive regions, where the foil actuator is mounted on the substrate. Recent investigations by digital image correlation demonstrate the formation and evolution of these regions [17]. For larger values of prestress (> 1.7 MPa) reversible actuation cycles are also observed.…”

Section: Resultsmentioning

confidence: 91%

“…So far, it is assumed that the foil actuator consists of a homogeneous material. Our results of magnetic field induced strain measurements analyzed by digital image correlation (DIC) suggest an inhomogeneous distribution of twinning stress [17]. The DIC investigations show that reorientation in the foil actuator occurs by formation and evolution of localized strain bands, the first of them forming at the relatively low field of about 0.1 T. For increasing magnetic field, the strain bands increase in size, while the twin boundary propagates through the specimen.…”

Section: Comparison With Experimentsmentioning

confidence: 77%

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A magnetic shape memory foil actuator loaded by a spring

Krevet

Pinneker

Kohl

2012

Smart Mater. Struct.

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This paper presents experimental and simulation results on the performance of a novel linear actuator that uses the magnetic shape memory (MSM) effect in a Ni-Mn-Ga foil device loaded by a mechanical spring. The linear MSM actuator shows reversible actuation cycles with maximum magnetic field induced strain change of 5.6% for optimized spring constant and prestress. The experimental results are compared with simulations based on a thermodynamics-based Gibbs free energy model. The model has been implemented in a finite element program, which uses beam elements and an integral magnetic solver. The simulations qualitatively describe the observed tensile stress dependence of the magnetostrain of the MSM foil actuator. We demonstrate that the effects of material inhomogeneity need to be taken into account to further improve the agreement with the experiment.

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Section: Resultsmentioning

confidence: 91%

Section: Comparison With Experimentsmentioning

confidence: 77%

A magnetic shape memory foil actuator loaded by a spring

Krevet

Pinneker

Kohl

2012

Smart Mater. Struct.

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“…11 Generally, Ni-Mn-Ga FSMAs are highly brittle in nature, hindering their use in practical applications. To overcome the brittleness of Ni-Mn-Ga alloys, various innovative fabrication routes have been introduced, resulting in melt-spun ribbons, 12 foils, 13 nanostructured powder, 14 plates, 15 composites, 7 thin films, 16 and foams. 17 Among these, synthesis of Ni-Mn-Ga alloy in thin-film form with significant ductility is of great interest because such materials are promising candidates for use in microelectromechanical system (MEMS) applications, for example, microactuators and microvalves.…”

Section: Introductionmentioning

confidence: 99%

Structural and Magnetic Properties of Sputter-Deposited Polycrystalline Ni-Mn-Ga Ferromagnetic Shape-Memory Thin Films

Kumar

Seenithurai

Raja

et al. 2015

Journal of Elec Materi

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Polycrystalline Ni-Mn-Ga ferromagnetic shape-memory thin films have been deposited on Si (100) substrates using a direct-current magnetron sputtering technique. The microstructure and the temperature dependence of magnetic properties of the films have been investigated by x-ray diffraction, scanning electron microscopy, and thermomagnetic measurements. As-deposited Ni 50.2 Mn 30.6 Ga 19.2 film showed quasi-amorphous structure with paramagnetic nature at room temperature. When annealed at 873 K, the quasi-amorphous film attained crystallinity and possessed L2 1 cubic ordering with high magnetic transition temperature. Saturation magnetization and coercivity values for the annealed film were found to be 220 emu/cm 3 and 70 Oe, respectively, indicating soft ferromagnetic character with low magnetocrystalline anisotropy. The magnetic transitions of the film deposited at 100 W were above room temperature, making this a potential candidate for use in microelectromechanical system devices.

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“…Homogeneous single-crystalline Ni-Mn-Ga alloys with only one twin boundary exhibit twinning stresses as low as 0.05 MPa [2]. Samples with a coarse twin structure are undesirable in many applications because they can kink extensively when strained and have a tendency to form intersecting twins which cause hardening [3,4] and fracture [5,6]. Samples with a dense twin structure remain straight when they are strained and can sustain hundreds of millions of loading cycles [1,5].…”

mentioning

confidence: 99%

Stabilizing a fine twin structure in Ni–Mn–Ga samples by coatings and ion implantation

2015

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The surfaces of Ni-Mn-Ga samples were coated with hard TiN and soft elastomer and implanted Nb + ions. All of these treatments stabilized a dense twin structure. After removing the treated surface layers, the original coarse twin structure reappeared. Compression tests of the ion-implanted sample with fine twins exhibited a continuously increasing, smooth stress-strain curve. Without the surface layer, the stress-strain curve was more rugged and flat, the twinning stress decreased, and one twin boundary moved throughout the entire sample.

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Evolution of local strain bands of different orientation in single crystalline Ni–Mn–Ga foils under tension

Cited by 15 publications

References 15 publications

A magnetic shape memory foil actuator loaded by a spring

A magnetic shape memory foil actuator loaded by a spring

Structural and Magnetic Properties of Sputter-Deposited Polycrystalline Ni-Mn-Ga Ferromagnetic Shape-Memory Thin Films

Stabilizing a fine twin structure in Ni–Mn–Ga samples by coatings and ion implantation

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