Magnetic field induced strains

April 25, 2010

[1] Magnetically resettable 0.16% free strain in polycrystalline Ni-Mn-Ga plates

M Pötschke et al

We investigated the microstructure, mechanical training and free strain due to magnetically induced reorientation (MIR) of a polycrystalline Ni50Mn29Ga21 alloy prepared by directional solidification, which showed columnar grains with a strong A fibre texture. Two-side mechanical training greatly decreased the twinning stress level of the properly cut plates. Consequently, a free strain of 0.16% has been observed in the trained plates and this strain is magnetically resettable for more than 20 times by rotating the magnetic field by 90°.

[2] Large magnetic-field-induced strain in Co-Ni-Al single variant ferromagnetic shape memory alloy

H Morito et al

At room temperature, Co41Ni32Al27 single-variant ferromagnetic shape memory alloy with a uniaxial magnetic anisotropy constant of –2.0 × 106 erg/cm3 exhibits a large magnetic-field-induced strain of 3.3% under a static compressive stress of about 10 MPa applied along the hard magnetization direction of the c-axis (c/a > 1). Compared with the data for other alloys, it becomes clear that a small change of twinning stress in the stress-strain curve is necessary for a large strain.

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