Texture and training of magnetic shape memory foam

Cassie Witherspoon; Peiqi Zheng; Markus Chmielus; Sven C. Vogel; David C. Dunand; Peter Müllner

doi:10.1016/j.actamat.2012.12.032

Texture and training of magnetic shape memory foam

Cassie Witherspoon, Peiqi Zheng, Markus Chmielus, Sven C. Vogel, David C. Dunand, Peter Müllner^*

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

20 Scopus citations

Abstract

Magnetic shape memory alloys display magnetic-field-induced strain (MFIS) of up to 10% as single crystals. Polycrystalline materials are much easier to create but display a near-zero MFIS because twinning of neighboring grains introduces strain incompatibility, leading to high internal stresses. Pores reduce these incompatibilities between grains and thus increase the MFIS of polycrystalline Ni-Mn-Ga, which after training (thermo-magneto-mechanical cycling) exhibits MFIS as high as 8.7%. Here, we show that this training effect results from a decoupling of struts surrounding pores in polycrystalline Ni-Mn-Ga during the martensitic transformation. To show this effect in highly textured porous samples, neutron diffraction measurements were performed as a function of temperature for phase characterization and a method for structure analysis was developed. Texture measurements were conducted with a magnetic field applied at various orientations to the porous sample, demonstrating that selection of martensite variants takes place during cooling.

Original language	English (US)
Pages (from-to)	2113-2120
Number of pages	8
Journal	Acta Materialia
Volume	61
Issue number	6
DOIs	https://doi.org/10.1016/j.actamat.2012.12.032
State	Published - Apr 2013

Keywords

Heusler alloys
Martensitic phase transformation
Neutron diffraction
NiMnGa
Thermal cycling

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Polymers and Plastics
Metals and Alloys

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10.1016/j.actamat.2012.12.032

Cite this

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title = "Texture and training of magnetic shape memory foam",

abstract = "Magnetic shape memory alloys display magnetic-field-induced strain (MFIS) of up to 10% as single crystals. Polycrystalline materials are much easier to create but display a near-zero MFIS because twinning of neighboring grains introduces strain incompatibility, leading to high internal stresses. Pores reduce these incompatibilities between grains and thus increase the MFIS of polycrystalline Ni-Mn-Ga, which after training (thermo-magneto-mechanical cycling) exhibits MFIS as high as 8.7%. Here, we show that this training effect results from a decoupling of struts surrounding pores in polycrystalline Ni-Mn-Ga during the martensitic transformation. To show this effect in highly textured porous samples, neutron diffraction measurements were performed as a function of temperature for phase characterization and a method for structure analysis was developed. Texture measurements were conducted with a magnetic field applied at various orientations to the porous sample, demonstrating that selection of martensite variants takes place during cooling.",

keywords = "Heusler alloys, Martensitic phase transformation, Neutron diffraction, NiMnGa, Thermal cycling",

author = "Cassie Witherspoon and Peiqi Zheng and Markus Chmielus and Vogel, {Sven C.} and Dunand, {David C.} and Peter M{\"u}llner",

note = "Funding Information: This project was funded by the National Science Foundation through grant NSF-DMR 1207192 (Boise State University) and DMR-1207282 (Northwestern University). M.C. acknowledges partial financial support through the German Research Foundation (DFG) priority program SPP 1239 (grant No. Schn 1106/1). P.M. is thankful to ETH Z{\"u}rich for donating magneto-mechanical testing devices. This work has benefited from the use of the Lujan Neutron Scattering Center at LANSCE, which is funded by the US Department of Energy{\textquoteright}s Office of Basic Energy Sciences. Los Alamos National Laboratory is operated by Los Alamos National Security LLC under DOE contract DE-AC52-06NA25396. ",

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doi = "10.1016/j.actamat.2012.12.032",

language = "English (US)",

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AU - Witherspoon, Cassie

AU - Zheng, Peiqi

AU - Chmielus, Markus

AU - Vogel, Sven C.

AU - Dunand, David C.

AU - Müllner, Peter

N1 - Funding Information: This project was funded by the National Science Foundation through grant NSF-DMR 1207192 (Boise State University) and DMR-1207282 (Northwestern University). M.C. acknowledges partial financial support through the German Research Foundation (DFG) priority program SPP 1239 (grant No. Schn 1106/1). P.M. is thankful to ETH Zürich for donating magneto-mechanical testing devices. This work has benefited from the use of the Lujan Neutron Scattering Center at LANSCE, which is funded by the US Department of Energy’s Office of Basic Energy Sciences. Los Alamos National Laboratory is operated by Los Alamos National Security LLC under DOE contract DE-AC52-06NA25396.

PY - 2013/4

Y1 - 2013/4

N2 - Magnetic shape memory alloys display magnetic-field-induced strain (MFIS) of up to 10% as single crystals. Polycrystalline materials are much easier to create but display a near-zero MFIS because twinning of neighboring grains introduces strain incompatibility, leading to high internal stresses. Pores reduce these incompatibilities between grains and thus increase the MFIS of polycrystalline Ni-Mn-Ga, which after training (thermo-magneto-mechanical cycling) exhibits MFIS as high as 8.7%. Here, we show that this training effect results from a decoupling of struts surrounding pores in polycrystalline Ni-Mn-Ga during the martensitic transformation. To show this effect in highly textured porous samples, neutron diffraction measurements were performed as a function of temperature for phase characterization and a method for structure analysis was developed. Texture measurements were conducted with a magnetic field applied at various orientations to the porous sample, demonstrating that selection of martensite variants takes place during cooling.

AB - Magnetic shape memory alloys display magnetic-field-induced strain (MFIS) of up to 10% as single crystals. Polycrystalline materials are much easier to create but display a near-zero MFIS because twinning of neighboring grains introduces strain incompatibility, leading to high internal stresses. Pores reduce these incompatibilities between grains and thus increase the MFIS of polycrystalline Ni-Mn-Ga, which after training (thermo-magneto-mechanical cycling) exhibits MFIS as high as 8.7%. Here, we show that this training effect results from a decoupling of struts surrounding pores in polycrystalline Ni-Mn-Ga during the martensitic transformation. To show this effect in highly textured porous samples, neutron diffraction measurements were performed as a function of temperature for phase characterization and a method for structure analysis was developed. Texture measurements were conducted with a magnetic field applied at various orientations to the porous sample, demonstrating that selection of martensite variants takes place during cooling.

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KW - Neutron diffraction

KW - NiMnGa

KW - Thermal cycling

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Texture and training of magnetic shape memory foam

Abstract

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