Mechanical training of polycrystalline 7M Ni50Mn30Ga20 magnetic shape memory alloy

Gaitzsch, Uwe; Pötschke, Martin; Roth, S.; Rellinghaus, Bernd; Schultz, L.

doi:10.1016/j.scriptamat.2007.05.026

Cited by 62 publications

(38 citation statements)

References 12 publications

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“…Before deformation the bicrystal was trained. The training route consisted in successively compressing the sample along all three axes in order to achieve maximum strain and to reduce the twinning stress and work-hardening rate [8].…”

Section: Methodsmentioning

confidence: 99%

Deformation twinning in polycrystalline NiMnGa alloys

Chulist¹,

Pötschke²,

Lippmann³

et al. 2010

J. Phys.: Conf. Ser.

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Abstract. The texture and local orientation after compression of a NiMnGa polycrystal and a bicrystal with 5M modulated structure were measured with synchrotron radiation and electron backscatter diffraction (EBSD), respectively. Compression of both samples leads to motion of those twin boundaries changing the volume fraction of particular martensitic variants in such a way that the shortest axis (c-axis) becomes preferentially aligned parallel to the compression axis. EBSD directly confirms the motion of twin boundaries within individual grains.

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Section: Methodsmentioning

confidence: 99%

Deformation twinning in polycrystalline NiMnGa alloys

Chulist¹,

Pötschke²,

Lippmann³

et al. 2010

J. Phys.: Conf. Ser.

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“…Foam II was cast from an alloy with composition Ni 52.2 Mn 24.1 Ga 23. 7 . Both foams are fully martensitic at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Due to constraints imposed by grain boundaries, the MFIS is near zero in randomly textured, fine-grained, polycrystalline Ni-Mn-Ga [6]. To reduce these constraints and increase MFIS, coarse-grained, highly-textured, polycrystalline Ni-Mn-Ga was produced by directional solidification and annealing [7]. These materials displayed a MFIS recovery of 1% after mechanical training [8], and a similar strain when magnetic actuation was combined with acoustic excitation [9].…”

Section: Introductionmentioning

confidence: 99%

Recent Developments in Ni-Mn-Ga Foam Research

Müllner

Zhang

Boonyongmaneerat

et al. 2009

MSF

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Abstract. Grain boundaries hinder twin boundary motion in magnetic shape-memory alloys and suppress magnetic-field-induced deformation in randomly textured polycrystalline material. The quest for high-quality single crystals and the associated costs are a major barrier for the commercialization of magnetic shape-memory alloys. Adding porosity to polycrystalline magneticshape memory alloys presents solutions for (i) the elimination of grain boundaries via the separation of neighboring grains by pores, and (ii) the reduction of production cost via replacing the directional solidification crystal growth process by conventional casting. Ni-Mn-Ga foams were produced with varying pore architecture and pore fractions. Thermo-magnetic training procedures were applied to improve magnetic-field-induced strain. The cyclic strain was measured in-situ while the sample was heated and cooled through the martensitic transformation. The magnetic field-induced strain amounts to several percent in the martensite phase, decreases continuously during the transformation upon heating, and vanishes in the austenite phase. Upon cooling, cyclic strain appears below the martensite start temperature and reaches a value larger than the initial strain in the martensite phase, thereby confirming a training effect. For Ni-Mn-Ga single crystals, external constraints imposed by gripping the crystal limit lifetime and/or magnetic-field-induced deformation. These constraints are relaxed for foams.

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“…Normally, directional solidification produces a fiber texture instead of a single component which is not sufficient to improve the shape memory properties. [9,10] Deformation may easily produce a single texture component if the deformation is sufficiently high. Due to the intrinsic brittleness of the FSMAs, texturation through heavy deformation is almost not possible.…”

mentioning

confidence: 99%

“…[17] This has well been proved by many experimental observations. [9,10,18] When the melted Ni-Co-Mn-In was jetted onto the surface of the copper wheel rotating at relatively low speed from the quartz tube, the nucleation of the crystallites starts from the surface of the copper wheel, as the copper wheel offers the highest undercooling due to the high thermal conductivity of copper and the necessary solid/ liquid interface for solidification. The radial direction of the wheel becomes a main heat transfer direction or thermal gradient direction.…”

mentioning

confidence: 99%

Texturation of Ni–Co–Mn–In Ribbons by Melt Spinning

Wang

Zhang

et al. 2010

Adv Eng Mater

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Ni45Co5Mn36.6In13.4 ribbons were prepared by the melt spinning technique. They are in the austenitic state at the room temperature with a Cubic L21 structure and are composed of columnar grains growing perpendicular to the ribbon plane. A nearly single {001}〈100〉 cube component is formed at low wheel‐rotating speed due to the preferential growth of nuclei in the ribbon plane normal and length directions. Appropriate control of the melt spinning condition offers a promising solution to the texturation of polycrystalline ferromagnetic shape memory alloys.

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Mechanical training of polycrystalline 7M Ni50Mn30Ga20 magnetic shape memory alloy

Cited by 62 publications

References 12 publications

Deformation twinning in polycrystalline NiMnGa alloys

Deformation twinning in polycrystalline NiMnGa alloys

Recent Developments in Ni-Mn-Ga Foam Research

Texturation of Ni–Co–Mn–In Ribbons by Melt Spinning

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